TrustedCalcs
Free finance calculators, developer tools and unit converters that show their working. Every result includes the formula behind it, and everything runs in your browser — your numbers never leave your device.
What it does
TrustedCalcs is a set of calculators for people who want to check the answer, not just get one. Every finance calculator shows the formula it used and where its inputs come from, so a mortgage repayment or an income-tax estimate can be traced back to the ATO, IRD, IRS or HMRC table it relies on.
Alongside finance there are developer tools — JWT decoding, hashing, Base64, regex, cron, timestamps, colour conversion, AES-GCM — and everyday unit converters. All of it runs in the browser: no account, no upload, no server-side processing of your numbers.
Each tool has a companion guide that explains the method in plain language, with regulatory citations where they apply, so the calculator is a starting point for understanding rather than a black box.
Platforms & pricing
Platforms
- Web — any modern browser, desktop or phone
- Localised editions for Australia, New Zealand, the United States and the United Kingdom
Pricing
- Price
- Free. No account, no paywall.
- Data
- Calculations run in your browser; nothing is sent to a server.
Pricing as shown on trustedcalcs.com on 2026-09-05; the product site is authoritative.
Your data, your call
- Your numbers never leave your device
- No account and no tracking of what you calculate
- Analytics on the site only with your consent