Online Arbitrage Software: What You Need and What to Skip

Last updated: September 2026

Most online arbitrage sellers who are overpaying for software are not using too many tools, they are using tools that solve problems they do not have yet while skipping tools that would solve problems they have right now.

A beginner who subscribes to an automated sourcing tool before they have sorted out their repricing floor is paying for faster product discovery on deals they cannot price correctly. A seller with 80 active ASINs who reprices manually because they do not see the value in a repricer is losing Buy Box time on every listing, every day, in the time between their manual checks.

The OA tool stack has three functions. The tools that belong in each function are well defined. The right question is not "which tools are best?" but "which function do I need to solve first, and which tools address it?"

TL;DR: OA software breaks into three functions: sourcing (finding products to buy), profit calculation (checking margins before purchase), and repricing (maintaining competitive prices after listing). Sourcing tools (Tactical Arbitrage, SourceMogul) and repricing tools (Repricer.com) solve different problems in sequence, not simultaneously. Beginners need a free profit calculator and Keepa before anything else. Automated sourcing and repricing both become necessary once manual processes cannot keep up, sourcing at around 50+ ASINs sourced per month, repricing at around 20+ ASINs listed. The minimum viable OA stack costs less than the margin recovered by setting the floor correctly on the first correctly priced lot.

The OA tool stack by function: sourcing, profit calculation, repricing

OA software has three distinct functions. No single tool covers all three. Confusing the functions, especially sourcing and repricing, leads to paying for the wrong tool at the wrong stage.

Function 1: Sourcing

Sourcing tools scan online retailers and match products against Amazon listings where a price difference creates a potential profit opportunity. They answer the question: which products should I buy?

Sourcing tools are not required to start OA. Beginners source manually by comparing retailer pages to Amazon directly. Sourcing tools become necessary when the manual research volume cannot keep up with the target buying rate.

Function 2: Profit calculation

Profit calculators take a product's sourcing cost, FBA fee, and referral fee and produce the estimated margin and the minimum selling price (floor) required to hit a target margin. They answer the question: is this specific product worth buying at this price?

Profit calculation is required before every purchase. The free Amazon FBA Revenue Calculator provides the FBA fee input for the floor formula. More advanced calculators produce persistent records and account for prep costs and inbound shipping.

Function 3: Repricing

Repricing tools monitor competitor prices on active FBA listings and adjust the seller's price to maintain competitive Buy Box positioning within the floor-to-ceiling range. They answer the question: is my price right now given what competitors are doing?

Repricing is not required for sourcing or for profit calculation. It becomes necessary when manual price monitoring cannot keep up with the rate of price changes on active listings, which happens at around 20+ active ASINs for most sellers.

Why sourcing and repricing are commonly confused:

Both tools interact with Amazon prices. Sourcing tools look at historical and current Amazon prices to identify opportunities. Repricing tools look at current Amazon prices to respond competitively. A sourcing tool does not monitor active listings after purchase, it is research infrastructure. A repricer does not find deals, it manages inventory that has already been sourced and listed.

Sourcing tools: Tactical Arbitrage, SourceMogul, and manual sourcing

Sourcing tools automate the product research process by scanning online retailer catalogues and comparing each product's cost to the Amazon marketplace price, applying the FBA fee to estimate the potential margin. They surface opportunities faster than manual browsing.

Keepa (essential at every stage):

Keepa is a price and BSR history tracker, not a sourcing tool in the traditional sense. It shows the history of the Amazon Buy Box price, the third-party new price, and the BSR over time for any ASIN. It is essential for two OA decisions:

First, validating whether a sourcing opportunity is real. If the current Amazon price for a product is $24.99 but the Keepa chart shows the price was $9.99 for most of the past 90 days with a recent spike, the "opportunity" is a price anomaly, not a stable margin. Buying at $14 sourcing cost to sell at $24.99 assumes the high price holds.

Second, ceiling-setting for repricing. The Keepa 90-day high is the evidence-based input for the maximum price in the repricing configuration. Setting the ceiling at the price the ASIN has actually sustained at historical Buy Box activity is more reliable than guessing. The online arbitrage repricing guide covers the ceiling-setting process in detail.

Keepa has a free tier with limited historical data and a paid tier with full history. For OA sellers who need 90-day price charts, the paid tier is necessary.

Tactical Arbitrage:

Tactical Arbitrage scans online retailer pages at scale, matches products to Amazon ASINs, applies FBA fees, and returns a list of potential profitable matches based on specified criteria (minimum ROI, minimum profit per unit, etc.). It covers hundreds of supported retailers and runs scans overnight, producing a prioritised buying list.

It is a sourcing tool: it finds products before they are purchased. It does not manage pricing after purchase and does not integrate with Amazon repricing.

When to use Tactical Arbitrage: when the target buying volume exceeds what manual research produces, and when the business is ready to evaluate opportunities in volume rather than one at a time. Beginners who have not yet worked through the buying, listing, and selling process manually are better served by understanding the workflow on a smaller scale before automating discovery.

When to skip it: in the first 1 to 3 months of OA, before the buying and selling workflow is established.

SourceMogul:

SourceMogul serves a similar function to Tactical Arbitrage, it scans a catalogue of supported retail sites and identifies potential Amazon FBA opportunities based on price difference and estimated fees. Different sellers prefer one or the other based on the retailer database, interface, and the way results are filtered.

The sourcing tool a seller uses is less important than having accurate profit calculations on the opportunities it surfaces. A sourcing tool that surfaces 100 deals, all calculated with incorrect FBA fees or missing prep costs, is less useful than one that surfaces 20 with accurate calculations.

When sourcing at scale with either tool: validate the profit calculation from the tool against the actual floor formula before purchasing. Sourcing tools estimate margins; the floor calculation for each lot uses the actual cost inputs, including prep and inbound shipping.

Profit calculators: the Amazon FBA Revenue Calculator and its limits

The Amazon FBA Revenue Calculator is the standard tool for checking margins before an OA purchase. It is free, accurate for FBA fee estimation, and available to all Amazon sellers at sellercentral.amazon.com. Its limitations are that it does not store calculations, does not account for prep costs or inbound shipping, and requires manual re-entry for every product checked.

What the FBA Revenue Calculator provides:

Enter an ASIN or product name and the expected selling price. The calculator returns:

FBA pick and pack fee (the per-unit fulfilment fee)
Monthly storage fee estimate
Referral fee
Net proceeds estimate

These are the inputs for the floor formula: (sourcing cost + prep + FBA fee) ÷ (1 minus referral fee rate minus target margin rate).

What the FBA Revenue Calculator does not provide:

Prep cost (the cost to inspect, sticker, and package units for FBA)
Inbound shipping to FBA warehouse
Storage duration assumptions for slow-moving stock
A persistent record of calculations across multiple products
Historical comparison of the current price against the 90-day range (Keepa provides this)

The floor formula as the correct calculation:

For OA sellers, the revenue calculator provides the FBA fee input. The floor formula builds the rest:

Floor = (sourcing cost + prep cost + FBA fee) ÷ (1 minus referral fee rate minus target margin rate)

At $9.50 sourcing cost, $0.80 prep cost, $3.18 FBA fee, 8% referral fee, 20% target margin: = ($9.50 + $0.80 + $3.18) ÷ (1 minus 0.08 minus 0.20) = $13.48 ÷ 0.72 = $18.72 minimum price

This floor is the minimum below which the repricer does not go, confirming it as accurate at purchase time prevents the margin erosion from incorrectly low floors. The Amazon seller fees guide covers the current fee schedule for different product size tiers.

Third-party profit calculators:

OAGenius and ArbitrageBoss are tools that integrate OA buying data with Amazon repricing. They allow sourcing cost data from buying runs to be imported directly into Repricer.com, so the floor is set from actual per-lot cost rather than re-entered manually. This integration is available from the Repricer.com integrations page.

Book a Demo, see how Repricer.com connects to OA workflows and receives floor data from OAGenius and ArbitrageBoss integrations.

Repricing tools: why OA sellers need automated repricing once inventory is listed

Once an OA product is listed on a competitive Amazon FBA listing, the Buy Box price changes continuously as other sellers on that listing reprice. A seller who checks prices manually once a day misses most competitive events. A repricer responds to those events within seconds.

What a repricer does that a sourcing tool does not:

A sourcing tool finds products before they are purchased. A repricer manages pricing after they are listed. These are separate phases with separate tools.

After listing, an OA ASIN enters a competitive environment with other FBA sellers. Amazon's Buy Box algorithm awards the Featured Offer (Add to Cart button) based on relative pricing and seller metrics. A seller who holds the lowest competitive price within the eligible set wins more Buy Box rotation time, which produces more sales.

Price changes on a competitive listing happen throughout the day as other sellers' repricers respond to events. A seller who checks prices manually at 8am and 8pm is effectively non-competitive during the hours between checks on active listings.

When repricing is necessary for OA sellers:

More than 20 active FBA ASINs listed simultaneously
Listed on categories with regular price movement (electronics, toys, health, home)
Listings with 3 or more active FBA sellers
Any listing where the sourcing cost is near the competitive price (thin margin = high risk of a manual check missing a floor breach event)

When manual repricing is still viable:

Under 20 ASINs, stable categories with infrequent price movement, and listings where the OA seller is the only FBA offer (thin-competition scenarios where there is no competitive event to respond to).

The floor in a repricer for OA:

For OA sellers, the floor is the most critical configuration in the repricer. It prevents selling below the per-lot sourcing cost. The floor varies per lot because OA sourcing costs change with each buying run. Setting the floor from the actual per-lot cost calculation (not a category estimate) is the difference between the repricer protecting margin and the repricer unknowingly selling below cost.

The online arbitrage repricing guide covers the per-lot floor calculation and the floor update workflow for each new buying run.

The minimum viable OA tool stack for beginners

A beginner OA seller, under 20 ASINs listed, under 50 units sourced per month, needs two free tools and one paid tool to operate the full sourcing-to-repricing workflow.

Minimum viable OA stack:

Keepa (free tier + optional paid): Purpose: price history validation before purchase, ceiling-setting for repricing. When to upgrade to paid: when the buying decisions require more than 90 days of price history or the free tier's limited data is producing missed opportunities. Skip it: never. Keepa is the single most important validation tool in OA. Buying without checking the price history on Keepa is buying without knowing whether the current opportunity is real.

Amazon FBA Revenue Calculator (free): Purpose: FBA fee input for the floor formula before each purchase. When to use: for every purchase, before committing. Skip it: never. A purchase without a profit calculation is not a business decision.

Repricer.com (paid, from 20+ active ASINs): Purpose: automated competitive repricing with a correct floor per ASIN. When to start: when the active ASIN count exceeds 20, or when any manually checked listing shows that the Buy Box price changed significantly between the last two manual checks. Skip it at: under 20 ASINs in stable categories with infrequent price movement.

Total cost at beginner stage: Keepa free tier (no cost), FBA Revenue Calculator (no cost), Repricer.com from the point the ASIN count warrants it.

What to skip at the beginner stage:

Automated sourcing tools (Tactical Arbitrage, SourceMogul): not necessary until manual sourcing is producing insufficient deal flow for the target buying volume. A beginner who has not yet learned to evaluate a deal accurately will produce poor-quality sourcing even with a tool surfacing 100 options, the decision quality is the bottleneck, not the discovery rate.

Advanced stack for sellers processing 100+ ASINs per month

An OA seller processing 100 or more ASINs per month has different bottlenecks: deal discovery, per-lot floor calculation, and post-listing repricing at scale. Each requires a specific tool.

Advanced OA tool stack:

Keepa (paid tier): At this volume, 90-day price history is required for every ASIN evaluated. The paid tier provides full history, rank history, and alerts for ASINs the seller is monitoring actively.

Automated sourcing tool (Tactical Arbitrage or SourceMogul): At 100+ ASINs per month, manual sourcing cannot produce the deal flow required. The sourcing tool runs scans overnight and returns a prioritised list of opportunities for evaluation. The seller's role shifts from discovery to evaluation: reviewing the sourced list, validating with Keepa and the floor formula, and making buying decisions.

At this stage, the quality of the buying criteria set in the sourcing tool matters significantly. An ROI threshold that is too low produces a long list of marginal deals. Too high and it produces a short list that misses viable inventory. The threshold calibration is based on the seller's actual costs per lot (including prep and inbound shipping), which the sourcing tool must be configured with accurately.

Repricer.com (essential): At 100+ ASINs listed simultaneously, manual repricing is not feasible. A repricer with correctly set floors per ASIN and correctly set ceilings from Keepa data is required. At this volume, the per-lot floor update process when new stock arrives, updating the minimum price for each ASIN to reflect the new lot's sourcing cost, is the most important maintenance task in the stack.

OAGenius and ArbitrageBoss integrations allow the floor to be imported directly from the sourcing data, reducing manual floor updates. These integrations are listed on the Repricer.com integrations page.

Inventory and P&L tool: At 100+ ASINs per month, tracking unit economics per ASIN and per lot requires a dedicated tool. Sellerboard, InventoryLab, and similar tools track cost of goods, FBA fees, and net profit per ASIN from the seller's actual data rather than estimates. These feed the floor calculation with accurate COGS per lot.

Net Margin Repricing allows P&L data to flow into the repricing floor automatically, so the floor recalculates when costs change rather than requiring manual updates after each new buying run.

Key Takeaways

OA software breaks into three functions: sourcing (finding products before purchase), profit calculation (checking margins at the point of purchase), and repricing (managing prices after listing). No single tool covers all three. Sourcing and repricing tools are sequential, not competing.
Keepa and the FBA Revenue Calculator are the two tools every OA seller needs. Keepa validates whether a price opportunity is real. The FBA Revenue Calculator provides the fee input for the floor formula. Both are free at entry level.
Repricing becomes necessary at around 20+ active ASINs. Manual price monitoring cannot match the rate of competitive events on FBA listings above this threshold. A repricer with correctly set floors is the tool that prevents selling at or below cost when competitors lower their prices.
Automated sourcing tools are last, not first. Tactical Arbitrage and SourceMogul solve a deal discovery bottleneck that typically does not appear until manual sourcing is producing insufficient flow, around 50+ ASINs per month target buying rate.
The floor is more important than the repricer rule type for OA sellers. An incorrect floor (one that omits prep cost or uses a stale FBA fee) results in the repricer protecting a margin that does not exist. Correct floor calculation per lot, updated with each new buying run, is the most important configuration in the OA tool stack.

Action Plan

Confirm that Keepa is installed and active for your product research workflow. If the free tier is limiting your ability to check 90-day price history, upgrade to the paid tier before the next buying run.
Confirm that the floor formula is being applied for every purchase decision, not only the FBA Revenue Calculator. The Revenue Calculator gives the FBA fee, the floor formula applies it correctly alongside sourcing cost, prep, and target margin.
Count your active FBA ASINs (currently listed and in stock). If above 20, set up Repricer.com with correct floors per ASIN from your most recent buying run costs. If below 20, make a note to evaluate repricing when the count crosses 20.
For each active ASIN in Repricer.com, confirm the current minimum price is set from the lot-specific floor formula (not a category estimate). The floor should reflect the actual sourcing cost of the units currently in FBA for that ASIN.
If processing more than 50 ASINs per month in sourcing: evaluate whether manual sourcing is producing sufficient deal flow. If not, run a trial of Tactical Arbitrage or SourceMogul for 30 days and compare output volume to the manual baseline.
Run the 10-point repricing configuration audit to confirm that floors and ceilings are correctly set across all active repricing ASINs.

Frequently Asked Questions

1. What software do I need for online arbitrage?

The minimum OA software stack has three components: Keepa for price history validation (free tier), the Amazon FBA Revenue Calculator for pre-purchase profit checking (free), and a repricer for managing prices after listing (necessary from around 20 active ASINs). Automated sourcing tools like Tactical Arbitrage or SourceMogul become necessary when manual sourcing cannot produce sufficient deal flow for the target buying volume, typically around 50 or more ASINs targeted per month. Sellers in the first few months of OA are generally better served by mastering the buying and selling workflow manually before adding sourcing automation.

2. Do I need a repricer for online arbitrage?

Yes, once you have more than 20 active FBA ASINs listed simultaneously. Below 20 ASINs in stable categories with infrequent competitive price changes, manual repricing is feasible. Above 20 ASINs, competitive price events on your listings occur at a rate that manual checking cannot match. A repricer with a correctly set floor (based on the per-lot sourcing cost plus all selling costs) prevents selling at or below cost when competitors lower their prices. The online arbitrage repricing guide covers the floor calculation and how to update it per lot.

3. What is the difference between an OA sourcing tool and a repricer?

A sourcing tool (Tactical Arbitrage, SourceMogul) helps you find products to buy by scanning retail sites and identifying price differences between retail and Amazon. It operates before purchase. A repricer (Repricer.com) manages the price of products you have already purchased and listed on Amazon, responding to competitor price changes to maintain Buy Box positioning within your floor and ceiling. The two tools address sequential stages of the OA workflow, sourcing, then repricing, and do not substitute for each other.

4. How do I build an efficient OA tool stack without paying for tools I do not use?

Add tools sequentially as the relevant bottleneck appears, starting with the two free tools (Keepa and FBA Revenue Calculator). The sequence: start with manual sourcing and the free tools. Add a repricer when active ASIN count exceeds 20 or when manual repricing is missing competitive events. Add an automated sourcing tool when manual sourcing cannot produce the buying volume you target. Add a P&L tool when you have more ASINs than the manual tracking of unit economics allows. Each tool addresses a specific bottleneck, adding a tool before the bottleneck appears is paying for a solution to a problem that does not exist yet.

Book a Demo, see how Repricer.com fits into the OA tool stack with integrations for OAGenius, ArbitrageBoss, and other OA workflow tools. See the features page for the full rule type and floor configuration options.