What we do

Free Online Calculators is a free library of purpose-built calculators for electrical, HVAC, mechanical, construction, materials, and physics work. Each tool answers one real question clearly, shows the formula it uses, and walks through a worked example, so you get an answer you can trust and understand.

Why we built it

Good calculations were scattered across spreadsheets, textbooks, and half-finished apps. We wanted one fast, free place where an engineer, tradesperson, or student could go from a question to a reliable answer in seconds, without sign-ups or paywalls.

How our calculators work

Every calculator runs entirely in your browser, so results are instant and your inputs stay on your device. The formulas are the recognised standards for each field, shown openly on each page alongside reference tables and common questions. We publish new tools regularly and keep the existing ones accurate.

A note on accuracy

Our tools are built for estimating, sizing, and checking work, and many professionals use them daily. For safety-critical or code-regulated designs, always confirm the result against the governing standard or a qualified professional.