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.
- Asphalt Calculator Hot-mix asphalt in tonnes for a drive or path, from the area and compacted thickness, with the sub-base underneath.
- Ballast Calculator Ballast needed for a concrete mix, by weight, volume and bulk bags.
- Baluster Spacing Calculator How many balusters a railing run needs and the exact centre spacing, so the gap never exceeds the limit and the end gaps match.
- Block Fill Grout Calculator Grout to fill the cores of a concrete block wall, by wall area and how many cores are filled.
Size a solar array, a generator, an air conditioner or a cable run.
- Antenna Length Calculator Physical length for a dipole, vertical, loop or 5/8-wave antenna at any frequency, including the end-effect correction.
- Battery Capacity Calculator The amp-hours and watt-hours a battery bank needs to run a given load for a given time, allowing for depth of discharge and inverter losses.
- 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.
Fuel, charging, towing, tyres and drivetrain maths.
- 0–60 Time Calculator An empirical 0–60 mph and 0–100 km/h estimate from power and weight. Within about a second for most road cars; it is a fit to data, not a simulation.
- Air-Fuel Ratio Calculator Converts between air-fuel ratio and lambda for any fuel, and says whether a mixture is rich or lean and what that means.
- Axle Load Calculator How a vehicle’s weight and a load split between the front and rear axles, from where the load sits, checked against the axle ratings.
- Bicycle Gear Calculator Gear ratio, gear inches and development for a chainring and sprocket combination, with the speed at a chosen cadence.
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.