About Calcflow

Calcflow is a privacy-first, ad-supported calculator hub. We build calculators that are fast, accurate and transparent — every formula is documented and every assumption is shown.

What we cover

• Finance: mortgages, loans, salary & tax for UK / India / Australia / US, savings, retirement and more.
• Health & fitness: BMI, calorie / TDEE, BMR, body fat, sleep cycles, pregnancy, ovulation, hydration, 1-rep max and macros.
• Math: percentages, age, date difference and GPA.
• Home & construction: concrete, paint and flooring estimators.

How we build calculators

1. Formulas first. We start from primary sources — HMRC, ATO, Indian Income Tax Department, peer-reviewed research, NIST.
2. Tested. Every calculator has unit tests asserting correctness against known cases.
3. Transparent. The formula and assumptions are visible on every page.
4. Private. All math runs in your browser. We never send your inputs to a server.

Tax-year disclosure

Tax brackets are kept current for the 2025/26 (UK), 2024-25 (Australia) and 2025-26 (India) financial years. US sales tax rates use state base rates and are clearly labelled.

Get in touch

Found a bug, have a calculator request or want to partner with us? Email hello@calcflow.cloud.