About apputil.com

Who is behind the site

apputil.com is edited and maintained by Rodrigo Brito, a software engineer who builds and reviews every tool published here. It is not a content farm and there is no automated publishing pipeline: each calculator is written by hand, tested against reference values and given an explanatory article before it goes live.

The project started as a personal collection of scripts used for day-to-day work — mortgage simulations, unit conversions, date arithmetic — and grew into a public library once it became clear that most online alternatives were either buried in ads or missing the explanation that makes a result useful.

What you will find here

The library covers ten areas: finance, health and fitness, unit conversion, developer utilities, dates, generators, text tools, mathematics, everyday calculations and construction. Every tool page combines three things: the working calculator, a plain-language explanation of the formula it uses, and a set of frequently asked questions covering the edge cases people actually run into.

• Finance — compound interest, loan amortisation, inflation, retirement projections
• Health — BMI, BMR, TDEE, body fat, macronutrients, heart-rate zones
• Conversion — length, weight, temperature, volume, speed, pressure, energy, data
• Developer — hashes, encoding, JWT parsing, subnets, cron expressions, formatters
• Everyday, dates, text, maths and construction — from tip splitting to concrete volume

How the tools are built and checked

Each calculator implements a documented, publicly verifiable formula. Where a standard exists — the WHO BMI ranges, the Mifflin-St Jeor equation for basal metabolism, the SI definitions for unit conversion, the standard amortisation formula for loans — we follow it and name it on the page, so you can check the method rather than trusting a black box.

Results are cross-checked against independent references before publication: spreadsheet implementations, official conversion tables and, where applicable, the published literature. When a formula has known limits (BMI ignores body composition; calorie estimates vary by roughly ten per cent between individuals) the page says so instead of presenting a single number as certainty.

Our full method, including how corrections are handled, is described in the editorial policy.

Privacy by design

Calculations happen entirely in your browser. The values you type into a calculator are never sent to our servers, because there is no server-side processing to send them to — the site is a set of static pages.

Your favourites and recently used tools are stored in your browser localStorage and stay on your device. We do use third-party services for audience measurement and advertising, which set their own cookies; those are described in detail in the privacy policy and the cookie policy, and you control them through the consent banner.

How the site is funded

apputil.com is free to use and funded by display advertising. Advertising pays for hosting, domains and the time spent writing and maintaining the tools. Advertisers have no influence over which tools we publish or what our articles say, and no article on this site is sponsored or paid for by a third party.

Languages

The whole site is available in English, Portuguese and Spanish. Translations are human-reviewed rather than machine-generated in bulk, and each language version links to its counterparts so search engines and readers can move between them.

Get in touch

Corrections, bug reports, tool suggestions and press enquiries are all welcome at [email protected]. If you believe a calculator returns a wrong result, tell us the inputs you used and the result you expected — those reports are the fastest way to improve the site.