DevFinanceTools is a collection of free, no-signup calculators for the money side of building software and freelancing. Everything runs in your browser — no account, no tracking beyond basic page-view analytics — and every tool shows its formulas and benchmarks so you can check the maths yourself.

Calculators

• SaaS Metrics — MRR, ARR, ARPA, gross & net revenue churn, NRR, GRR, LTV, CAC, LTV:CAC, CAC payback and the Quick Ratio from one month of data, each with a benchmark.
• Freelance Hourly Rate — works backwards from the take-home income you want, through unbillable time, expenses and tax, to the rate you need to charge.
• Subscription Cost — list your recurring subscriptions and see the real total per month, per year and over five years. Saved in your browser only.
• Uptime / SLA — turn an availability target like 99.9% into exact downtime per day, week, month and year, and back again.
• Cost of Downtime — estimate what an outage costs in lost revenue, lost productivity and recovery, as a total and per minute.
• Inflation — what a US dollar amount from one year is worth in another (CPI-U), with cumulative and average annual inflation.
• Savings Goal — how much to save each month to hit a target by a date, or how long a fixed amount will take.
• Hourly ↔ Salary — convert between an hourly rate and yearly, monthly and weekly pay, both directions.
• Compound Interest — project a starting amount plus regular contributions, with a year-by-year breakdown.
• LLM API Cost — estimate what an AI feature costs per request, day and month from token prices and volume, including prompt-caching savings.

There are also short plain-English guides on the topics behind the tools.