Free Online Calculators
Enter your numbers, get the answer, and see how it was reached — plus what to do with it. Units convert as you type, and every result is a link you can send someone.
Work out how much concrete, gravel, paint or tile a job needs — and what it will cost.
- Concrete Bag Calculator How many bags of concrete a volume needs — 80 lb, 60 lb, 40 lb, 25 kg and 20 kg side by side, with the total weight to carry.
- Concrete Column & Pier Calculator Concrete for round or square columns and piers — volume per column, total, bags, weight and cost.
- Concrete Driveway Calculator Concrete needed for a driveway — volume, bags, weight and cost, at the thickness a vehicle actually needs.
- Concrete Footing Calculator Concrete for strip footings and pad foundations — total volume, bags, weight and cost for a trench run or a set of pads.
Size a solar array, a generator, an air conditioner or a cable run.
- Battery Charge Time Calculator How long a battery takes to charge from a given state of charge, at a given charger current.
- Battery Runtime Calculator How long a battery will run a load, accounting for usable depth of discharge and inverter efficiency.
- Electricity Cost Calculator What an appliance costs to run — per day, month and year — from its wattage, hours of use and your unit rate.
- Generator Size Calculator Size a generator from running watts and starting surge, with the fuel it will burn per hour.
Fuel, charging, towing, tyres and drivetrain maths.
- Cost Per Mile Calculator The true running cost of every mile — fuel plus servicing, tyres, insurance and depreciation.
- EV Charging Cost Calculator What it costs to charge an electric car — including the charging losses you pay for but never store.
- EV Charging Time Calculator How long an electric car takes to charge, from the charger power, battery size and the charge you are adding.
- EV Range Calculator Real-world range from battery size and consumption, with the effect of speed, cold and a usable-charge reserve.
Units, measures and standards.
- Angle Converter Convert between degrees, radians, gradians, turns, arcminutes and arcseconds.
- Area Converter Convert between square metres, square feet, acres, hectares and square miles.
- Data Storage Converter Convert between bits, bytes, kilobytes, megabytes, gigabytes, terabytes and their binary equivalents.
- Density Converter Convert between kg/m³, g/cm³, kg/L, lb/ft³, lb/in³ and lb/yd³.