See the difference, not just the number
Free tools that do one job well: engineering calculators for solar, heating and cooling, wiring, concrete and bolts; comparisons drawn to scale; a name wheel and a timer for the classroom. Nothing to install, no account, everything runs in your browser.
- Size ComparisonPeople, animals, vehicles, buildings and planets side by side, to scale.
- Screen Size ComparisonPhones, tablets, laptops, monitors and TVs: real width, height and area.
- Weight ComparisonHow heavy is X compared to Y, and how many Y make one X.
- Random Name PickerSpin a wheel of names with no repeats, then split the same list into groups.
- Classroom Timer and StopwatchFull-screen countdown with a colour ring, or a stopwatch with laps. Both keep time in the background.
- Random Number GeneratorOne number or a thousand between any two values, with or without repeats.
- Coin FlipA fair heads or tails, with a running tally and a flip-many mode.
- Time Zone ConverterConvert a time between two cities, or find a meeting hour across New York, London, Singapore and Sydney.
- Crossword PuzzlesA new crossword every day at easy, medium and hard, in English, Spanish, French or German.
- Crossword & Anagram SolverFind words by pattern (c?o?s), from your letters, or that start, end or contain something. Wordle helper too.
- Word CounterWords, characters, reading time and readability as you type; HTML to plain text for listings.
- Solar Panel & Battery CalculatorHow many panels and how much battery for your usage and city, with annual output and payback.
- BTU & Heat Pump Sizing CalculatorCooling and heating load for a room or whole house in BTU, tons and kW, with the unit size to buy.
- Wire Size & Voltage Drop CalculatorMinimum AWG or mm² for a circuit from ampacity and voltage drop, copper or aluminium, DC to three-phase.
- Concrete & Rebar CalculatorCubic yards, m³, bag counts and rebar for slabs, footings, walls, columns and post holes.
- Mortgage CalculatorMonthly payment with tax, insurance and PMI, total interest, extra payments and a full amortization schedule. US, UK, Canada, Australia.
- QR Code GeneratorQR codes for links, Wi-Fi, contacts, email and text. Custom colours, PNG and SVG download, never expires.
- BMI CalculatorBody mass index in metric or imperial, with the healthy weight range for your height and Asian cut-offs.
- Image ResizerResize, crop to a preset and compress JPG, PNG and WebP to a target size. Images never leave your device.
- Bolt Torque CalculatorTightening torque and clamp force for metric and imperial bolts by grade, lubrication and preload.
Why pictures
Numbers on a spec sheet are hard to judge. A 65-inch TV has about twice the screen of a 46-inch one; a blue whale weighs as much as 25 elephants; a Boeing 737 is seven people tall. Drawn to the same scale, the difference is obvious in a second. New tools are added every couple of weeks; if there is a comparison you wish existed, tell us.