All tools
32 free tools, no sign-up
Everything runs in your browser — nothing you type is sent to a server. Results are estimates for planning, not safety approvals: always check your door-jamb placard, load index and speed rating before changing tyre size.
Tyre tools
Tyre sizes, pressures, tread, load index and speed rating — everything about the four patches of rubber that hold your car to the road.
Tyre Size Calculator
Decode any tyre size
Tyre Size Comparison
Compare two tyre sizes
Speedometer Error Calculator
Actual speed after a tyre change
Plus Sizing Calculator
Plus-one and plus-two fitments
Tyre Pressure Calculator
Pressure by load — estimate
Tyre Age Checker
DOT date code to tyre age
Tyre Tread Depth Calculator
Remaining tread vs the legal limit
Tyre Load Index Calculator
Load index to kg and back
Tyre Speed Rating Calculator
Speed rating to max speed
Tyre Size Converter
Metric to flotation sizes
Fuel & running-cost tools
MPG, fuel cost, trip cost, EV comparisons and CO₂ — what your car costs to run, per mile and per year.
MPG Calculator
Miles per gallon
Fuel Cost Calculator
Cost of a tank or a trip
Trip Cost Calculator
Fuel plus tolls for a trip
EV vs Petrol Calculator
Electric vs petrol running cost
Fuel Economy Converter
MPG to L/100km and back
CO2 Emissions Calculator
CO2 from your driving
Diesel vs Petrol Calculator
Which fuel costs less per year
Fuel Tank Range Calculator
How far on a full tank
Cost Per Mile Calculator
All-in running cost per mile
Annual Fuel Cost Calculator
Yearly fuel bill
Performance tools
Gear ratios, rpm, towing, braking distance and quarter-mile estimates — the numbers behind how a car moves.
Gear Ratio Calculator
Ring and pinion ratio
RPM Speed Calculator
Engine rpm at road speed
Towing Capacity Calculator
Can you tow that trailer?
Tyre Cost Per Mile Calculator
Tyre wear cost per mile
Wheel Offset Calculator
Offset, ET and backspacing
Bolt Pattern Calculator
PCD from lug count
Tyre Diameter Calculator
Overall diameter from width and aspect
Revs Per Mile Calculator
Tyre revolutions per mile
Braking Distance Calculator
Stopping distance, dry and wet
Horsepower Torque Calculator
HP to torque and back
Quarter Mile Calculator
Rough ET and trap speed
Payload Calculator
GVWR minus curb weight
Not sure where to start?
Most people come for one of three things: decoding the size on their tyre sidewall, checking whether a different size will fit, or working out what a trip will cost in fuel. Start with the tyre size chart, the tyre size guides or the fuel cost guides. If you want the numbers behind the tools, the chart lists all 326 common tyre sizes with diameter, sidewall height and circumference.
Prefer reading to calculating? The guides cover the same ground in depth: tyre sizes explained, size comparisons, speedometer accuracy and MPG guides.