Free tools for SaaS founders.
Calculators for the two questions every SaaS runs into: what your payment provider really takes, and whether the business behind it is healthy. Every tool runs in your browser and shows its formula.
Free · No sign-up · Nothing you type leaves your browser
Payment fee calculators.
What Stripe, PayPal and the merchants of record really take from a sale, with rates checked against each provider's own pricing page.
- Start herePayment fee comparisonStripe, PayPal, Polar, Paddle, Lemon Squeezy, Creem, Dodo Payments, Gumroad and Whop side by side on the same sale, including international cards and tax.
- Stripe fee calculatorStripe's fee and your payout for any amount, or what to charge to keep a target. US, EU and UK pricing with Billing, Tax and Managed Payments.
- PayPal fee calculatorPayPal's fee on goods and services, checkout and card payments, what you receive, and what to charge to receive an exact amount.
- Polar fee calculatorPolar.sh fees on every plan, from Starter to Scale, and the plan that costs least at your volume.
- Paddle fee calculatorWhat Paddle's 5% + 50¢ costs on your price, and how it compares with Stripe and the other merchants of record.
- Lemon Squeezy fee calculatorLemon Squeezy's base fee plus its international, subscription and PayPal surcharges, and what you keep.
- Dodo Payments fee calculatorDodo Payments' 4% + 40¢ plus its international and subscription surcharges, and what you keep from each sale.
- Gumroad fee calculatorGumroad's 10% + 50¢ plus card processing on direct sales, or 30% through Discover, and what you keep.
- Whop fee calculatorWhop's 2.7% + 30¢ card fee with international, currency and tax-service add-ons, and what you keep.
SaaS metrics calculators.
The numbers investors and acquirers ask about, with the formulas shown and the edge cases handled.
- LTV calculatorCustomer lifetime value from ARPA, gross margin and churn, with LTV:CAC, payback and a discounted LTV that survives 0% churn.
- CAC calculatorBlended customer acquisition cost, CAC payback in months and LTV:CAC from your sales and marketing spend.
- Churn rate calculatorCustomer churn, compounded annual churn, gross and net MRR churn, GRR and NRR from one set of numbers.
- MRR calculatorMonthly recurring revenue from your plans, and net new MRR from new, expansion, contraction and churned revenue.
- ARR calculatorConvert MRR to ARR and back, and get year-over-year ARR growth and your Rule of 40 score.
Other tools.
Small browser tools for content and mockups.
Pick a payment provider. Keep your code.
SyntaxKit is a Next.js SaaS starter kit with billing already built. Start on Stripe, Polar or Creem and switch later with one setting: your plans, checkout and access rules stay exactly the same.
- Hosted checkout and customer portal
- Plans, prices and feature limits in one file
- Webhooks that stay correct when retried
- Per-seat plans, and usage billing on Stripe
- Refunds and disputes end access automatically
- Invoices and AI usage on the billing page
From $199 · one-time payment · lifetime updates
Payment provider
- Free3 projects$0/mo
- ProUnlimited projects, AI chat$29/mo
- Team5 seats, roles and invites$79/mo
Checkout byStripe
Same plans, same checkout code