GrowthMath

GrowthMath is a free set of 21 calculators for people who buy traffic, run affiliate programs or sell online: ROAS and break-even ROAS, CPM/CPC/CPA, break-even CPA, affiliate EPC and revenue leak, customer LTV, CAC, churn, Shopify profit, YouTube earnings, engagement rate, A/B test significance and sample size, a UTM builder and a SERP snippet preview.

Every tool shows the formula, benchmarks and what the result means - not just a number. There is no signup, calculations run locally in the browser, and any calculator can be embedded on your own site for free with a short HTML snippet.