Calculators
Straight number-crunching for performance, fuel, gearing and running costs - enter your figures and get the answer.
0-60 Calculator
Power, weight and drivetrain to an estimated 0-60mph and 0-100km/h, with AWD/FWD traction adjustment.
Displacement & Compression
Bore, stroke and cylinders to exact cc, plus compression ratio from clearance volume, with the formulas shown.
EV Charging Cost Calculator
Battery size, tariff and efficiency give you pence per mile, full charge cost, range and miles per pound.
Journey Fuel Cost
Distance, MPG and pence per litre give you the true cost of a trip, per mile and per person, before you set off.
Gear Ratio Speed Calculator
Gear ratios, final drive and tyre size in; mph per 1000rpm, speed at redline in every gear, and cruising rpm out.
Oil Service Cost Calculator
Enter your oil capacity and today's prices to get an exact service cost, DIY against a garage quote.
Power to Weight Calculator
Power in bhp, kW or PS and weight in kg to bhp/tonne, kW/tonne and W/kg, with rough performance bands.
Wheel Speed Calculator
Road speed to wheel rpm and back, for your exact tyre size, with a reference table for common speeds.
Comparators
Line two options up side by side - tyres, wheels, brakes or charging tariffs - and see exactly what changes.
Brake Disc Comparator
Compare two disc sizes: braking torque gain from the longer lever arm, swept area and thermal mass, drawn to scale.
EV vs Petrol Cost Comparator
Compare a petrol car's MPG against an EV's efficiency for pence per mile, annual saving and the break-even electricity price.
Home vs Public Charging Comparator
Line up to four charging tariffs side by side, from cheap overnight rates to public rapid DC, cost per mile and per charge.
Tyre Size Comparator
Compare two tyre sizes: diameter change, speedo error, ride height and the ±3% verdict, with both tyres drawn to scale.
Wheel Offset Comparator
Enter two width and ET combinations and see exactly how far the new wheel moves toward the arch or the suspension, in millimetres.
Converters
Switch between units instantly - power, torque, pressure and fuel economy - with the exact conversion factors used.
kW to BHP Converter
Convert kW to bhp and PS instantly, and back again, with exact factors and a worked example.
MPG to L/100km Converter
Convert mpg to l/100km and UK to US mpg, all synced live using exact gallon factors.
Torque & Power Converter
Nm, lb-ft, bhp, PS and kW, all synced live, plus power calculated from torque and rpm with the exact dyno formula.
Tyre Pressure Converter
Psi, bar and kPa, all synced live, with a quick reference table for common pressures.
Checkers
Confirm fitment and limits before you commit - bolt patterns that match, and towing figures that stay legal.
Bolt Pattern (PCD) Checker
Compare two bolt patterns and see instantly whether they match, plus adjacent-hole spacing for measuring a wheel by hand.
Towing & Payload Checker
Every towing limit checked at once: payload, capacity, gross train weight, noseweight and the 85% stability guideline.
Guides
Explainers and worked examples to go with the calculators above, for when you want the reasoning as well as the number.
Gear Ratios Explained
How gear ratios and final drive combine to set torque, road speed and acceleration, with a worked example.
Tyre Speed Rating Chart
Speed rating letters N to Y in mph and km/h, plus a load index chart in kg per tyre.
5W-30 vs 5W-40
What the SAE numbers mean, when each grade is specified, and why the handbook approval code matters too.
Towing Capacity Explained
Kerb weight, MAM, gross train weight and noseweight defined, plus the 85% caravan guideline.
About CalcGarage
Every tool on this site works from published formulas and defined conversion factors, so the answer you get is the answer, not an estimate or an opinion. Each page explains the maths it uses and, just as importantly, what it can't tell you, because a calculator that hides its limits isn't a tool, it's a guess with a nice interface.
No accounts, no data collection beyond standard analytics, and everything runs in your browser. If a tool you need is missing, or a result looks wrong, get in touch through the contact page.