Universal Unit Converter,
Calculator & Reference Tool
A free, comprehensive tool for length, mass, temperature, volume & more. Convert, calculate, and explore 450+ units across 36 categories.
Works 100% Locally
Your conversions never leave your device. No servers, no tracking, no data collection.
Works Offline
No internet required after initial load
No Data Uploads
All calculations stay on your device
No Login Required
Start converting immediately
Convert, Calculate & Visualize Units Instantly
Multiple modes for different needs—from quick lookups to detailed reference tables.
Simple Mode
Quick conversions with auto-format and instant results
Advanced Mode
Multi-step calculations with precision control
Reference Mode
View conversion tables and formulas
36 Categories & 450+ Units
From everyday measurements to scientific calculations
More Features
Who Is This For?
Students
Science, math, engineering homework and assignments
Engineers
Technical calculations and precision work
Professionals
Quick daily conversions for work
Scientists
Research calculations and unit verification
Popular Conversions
Quick links to the most searched unit conversions worldwide
From the Blog
Read all articlesThe Metric System: A Beginner's Guide
Learn the fundamentals of the metric system, its base units, prefixes, and why it's the global standard for scientific measurements.
Imperial vs Metric: Why the World Uses Different Systems
Explore the historical origins of imperial and metric systems, and understand why some countries still use imperial measurements.
How to Convert Celsius, Fahrenheit & Kelvin
Master temperature conversions with clear formulas, examples, and understand when to use each temperature scale.
How UnitConvertLab works
1. Pick a category, or just type
Choose one of 36 categories — length, mass, temperature, volume, area, speed, pressure, energy, data, fuel economy, typography, blood sugar, shoe size, wire gauge and more — or press Ctrl+K and type a plain-English query such as "5 km to miles" or "180 C in F". The parser understands symbols, plurals, abbreviations and compound inputs like 5 ft 11 in.
2. The conversion runs in your browser
Your value is converted to the category's SI base unit, then out to the target unit, at full double precision. Nothing is sent to a server, so results appear as you type and the whole app keeps working on a plane, on a site with no signal, or after you install it as an offline app.
3. See the formula, not just the number
Every result is shown with the formula that produced it, the exact conversion factor, a worked example and a reference table of common values. Adjust the displayed precision, swap the direction in one tap, save the pair to favourites, or copy a shareable URL that reopens the exact same conversion.
Who UnitConvertLab is for
UnitConvertLab is built for people whose numbers have consequences: engineers and drafters moving between metric and imperial drawings, students checking homework against a shown formula, nurses and clinicians converting doses, weights and blood-sugar readings, cooks scaling recipes between grams, cups and millilitres, machinists working in thousandths, and land buyers in South Asia, East Asia and the Middle East reconciling a bigha, tsubo or dunam with hectares and acres.
What makes it different is provenance. Most converters give you a number and no way to check it. Every factor here is traced to a primary standard — the BIPM SI Brochure, NIST SP 811, ISO and IEC standards, or the national authority that defines a traditional unit — and each page states the source, the verification date and any known regional variation. Corrections are logged publicly rather than quietly edited, and the underlying data is available as open JSON for anyone who wants to audit or reuse it.
It stays free, needs no account, shows no interstitial ads, and stores your preferences only in your own browser. If a unit or a category you rely on is missing, or a factor looks wrong for your region, tell us — regional accuracy comes from the people who use those units every day.