---
title: "Free calculators for buyers of small online businesses"
url: https://firstpassmemo.com/tools/
updated: 2026-10-07
publisher: FirstPass Memo (hello@firstpassmemo.com)
---

Calculators

# Free calculators for buyers of small online businesses

Five calculators for the arithmetic that listing pages leave to you. Each one runs in your browser, sends nothing you type, and keeps your inputs in the page address so you can bookmark or share a result.

## True payback calculator (https://firstpassmemo.com/tools/payback-calculator/)

Headline payback and multiple, then the same figures after the owner's time, costs missing from the P&L and one-time deal costs.

## SaaS churn stress test (https://firstpassmemo.com/tools/saas-churn-stress-test/)

MRR over the next 12 months at the stated churn rate, and payback if new sales continue or stop after you take over.

## Traffic-drop test (https://firstpassmemo.com/tools/traffic-shock-test/)

Profit and payback after a fall in organic search revenue, and the size of drop that takes profit to zero.

## Amazon FBA price check (https://firstpassmemo.com/tools/fba-inventory-price-check/)

The multiple as listed, the multiple once inventory is counted, and how many months of sales the stock covers.

## Seller financing calculator (https://firstpassmemo.com/tools/seller-financing-calculator/)

The monthly note payment, the cash left from profit each month and how long it takes to earn back your down payment.

Have a listing open? The red-flag checker (https://firstpassmemo.com/checker/) reads the listing text, works out payback and lists the top flags with a question for the seller on each. For a full memo on a live listing priced $10k–150k, apply for the free beta (https://firstpassmemo.com/#beta).

The calculators do arithmetic on the figures you enter. They are not investment, legal, tax or valuation advice, and they do not check whether a seller's figures are true.

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FirstPass Memo is informational screening, not investment, legal, tax, accounting or valuation advice, and not an audit. Seller figures are not independently verified. HTML version: https://firstpassmemo.com/tools/