Calculate anything,
instantly.
Effortlessly convert units, currencies, and more with our comprehensive range of simple-to-use calculators and converters.
Fullscreen Calculator
The online calculator that just works.
No clutter. No ads. No distractions. A clean, fast calculator available free in your browser — or expand it to fullscreen for total focus.
All Tools
Every calculator you need.
From everyday arithmetic to specialist converters — all free, all instant, all beautifully simple.
Simple Calculator
Fast, clean everyday calculator for basic arithmetic.
Scientific Calculator
Trig, logarithms, powers and advanced maths functions.
Fullscreen Calculator
Distraction-free fullscreen mode — perfect on any screen.
Online Abacus
Interactive abacus for learning and mental arithmetic.
BMI Calculator
Calculate your Body Mass Index with metric or imperial units.
Percentage Calculator
Work out percentages, discounts and percentage changes.
Patio Calculator
Calculate materials, area and cost for patio and tiling projects.
Darts Calculator
Real-time darts scorer and checkout calculator for all formats.
Maths Calculator
Equations, algebra, fractions and advanced maths tools.
Length Converter
Metres, feet, inches, miles, km and more.
Weight Converter
Kilograms, pounds, stone, ounces and all weight units.
Temperature Converter
Celsius, Fahrenheit, Kelvin conversions instantly.
Speed Converter
MPH, km/h, m/s, knots and aviation speed units.
Volume Converter
Litres, gallons, fluid ounces, cups and more.
Time Converter
Seconds, minutes, hours, days, weeks and years.
Ring Size Converter
UK, US, EU and international ring size charts.
Why SpotOn
Built for speed. Designed for clarity.
Why we're different
Everything your competitors get wrong, we got right.
Instant results
No page reloads. Every calculation and conversion updates live as you type.
Works everywhere
Fully responsive on any device. No app download needed — open and use.
Private by default
Everything runs in your browser. No data sent to servers, no tracking.
Clutter-free UI
Clean, distraction-free design. No pop-ups, no upsells, no noise.
Accessible
Full keyboard support and screen reader compatibility built in from day one.
SEO-optimised
Each tool has its own fast-loading page, perfect for bookmarking or sharing.
Ready to calculate?
Pick a tool and start instantly. No sign-up, no download, no cost.