About billycalc
billycalc is a free online calculator service designed to help anyone make informed decisions in finance, health, construction, marketing and other areas. We believe everyone should have access to accurate calculations via transparent formulas.
Our principles
- 100% free forever — all 5800+ calculators are available without subscription, signup or payment
- Transparent formulas — every calculation uses publicly known formulas from official sources (Central Bank rates, WHO standards, engineering codes)
- Privacy by default — all calculations run in your browser. The numbers you enter are NEVER sent to our server
- No ads inside calculators — monetization only on blog pages and through partner affiliate offers
Formula sources
We use formulas from:
- Central banks and financial regulators for finance calculators
- WHO and medical research for health calculators (BMI, BMR, TDEE)
- Building codes (SNiP, ASTM, ACI) for construction calculators
- Academic textbooks for math, physics and engineering
English pilot
Currently we have 5 calculators in English (Loan, Mortgage, BMI, Compound Interest, Sales Tax). The Russian version has 5800+ calculators across 14 categories. We're gradually expanding English coverage.
Help us localize — feedback welcome
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