cyclesizing
Calculators for people who count teeth, watts and millimetres.
Free cycling calculators for gear ratios, bike fit, tire pressure, suspension setup and watts.
Bike fit and geometry
Frame size, saddle, bars, stem and cleats.
Bike fit and geometry
Bike Frame Size Calculator
Estimate road, gravel or MTB frame size in centimetres from inseam and height. Inseam sets the size; height only nudges the rounding.
Bike fit and geometry
Stack and Reach Ratio Calculator
Divide frame stack by reach. Below 1.45 is race (under 1.35 very aggressive), from 1.45 up to 1.55 is a sporty all-rounder, and 1.55 or higher is upright endurance.
Bike fit and geometry
Optimal Saddle Height Calculator
LeMond saddle height is 0.883 times inseam, measured from the centre of the bottom bracket to the top of the saddle.
Bike fit and geometry
Handlebar Width Calculator
Match road bar width to shoulder width and add 20 mm for gravel. A flat MTB bar is measured end to end: about 1.9 × shoulder width, kept within 720–800 mm.
Bike fit and geometry
Crank Length Calculator
Map inseam to cranks from 160 to 177.5 mm in 2.5 mm steps, plus a shorter modern alternative.
Bike fit and geometry
Stem Length and Angle Calculator
See how stem length, stem angle and head tube angle add horizontal reach and vertical rise on top of frame reach.
Bike fit and geometry
Cleat Fore-Aft Calculator
Estimate foot length from an EU shoe size and place the cleat centre near the ball of the foot.
Drivetrain and gearing
Ratios, rollout, chain length and cassette range.
Drivetrain and gearing
Bicycle Gear Ratio Calculator
Gear ratio is chainring teeth divided by cassette cog teeth. Compare the easiest and hardest gears for real chainring and cassette pairs.
Drivetrain and gearing
Gear Inches and Roll-out Calculator
Convert a chainring and cog plus wheel size into gear inches and metres travelled per pedal revolution.
Drivetrain and gearing
Optimal Chain Length Calculator
Estimate chain links from chainstay length, the largest chainring and the largest cassette cog. Rounded up to an even link count.
Drivetrain and gearing
Derailleur Capacity Calculator
Total capacity is the chainring difference plus the cassette difference. See whether a short, medium or long cage is enough.
Drivetrain and gearing
Cadence to Speed Calculator
Turn cadence, chainring, cog and wheel size into speed. Roll-out per revolution times cadence gives km/h.
Drivetrain and gearing
Cassette Range Calculator
Cassette range is the largest cog divided by the smallest, times 100. A 10–52 is 520%.
Drivetrain and gearing
Fixie Skid Patch Calculator
Skid patches are the cog divided by its greatest common divisor with the chainring. They double for either-foot skidders when the reduced chainring is odd.
Wheels and tires
Pressure, spokes, sealant, ETRTO and circumference.
Wheels and tires
Tire Pressure Calculator
Starting tyre pressure from system weight, tyre width and surface. Front and rear are split, and hookless rims cap at 72.5 psi.
Wheels and tires
Spoke Length Calculator
Spoke length from rim ERD, flange diameter, offset, spoke count and cross pattern. One side per calculation.
Wheels and tires
Tubeless Sealant Calculator
Estimate tubeless sealant in millilitres from tyre width and bead-seat diameter. Wider tyres and 29-inch wheels take more fluid.
Wheels and tires
Rim and Tire ETRTO Checker
Check a tyre width against an inner rim width with the ETRTO 2024 table. A yes means that pairing is listed for the rim.
Wheels and tires
Wheel Circumference Calculator
Wheel circumference in millimetres from bead-seat diameter and tyre width. Use it to calibrate a speed sensor.
Suspension and MTB setup
Sag, coil rate, rotors and flip chips.
Suspension and MTB setup
Fork Sag and PSI Calculator
Sag in millimetres from travel and a target percent, plus a starting air pressure from rider weight.
Suspension and MTB setup
Rear Shock Spring Rate Calculator
Estimate a coil spring rate in lb/in from rider weight, leverage ratio, stroke and target sag.
Suspension and MTB setup
Brake Rotor Size Calculator
Pick a front and rear rotor diameter from rider weight and discipline: road, gravel, trail, enduro or downhill.
Suspension and MTB setup
Flip-Chip Geometry Calculator
See a typical flip-chip change: 0.5° slacker head angle and 6 mm lower bottom bracket in the low position.
Performance and e-bikes
W/kg, VAM, drag, range, fueling and torque.
Performance and e-bikes
E-Bike Battery Range Calculator
Estimate e-bike range from battery watt-hours, assist level and average gradient. Uses 90% of the pack.
Performance and e-bikes
Power-to-Weight Calculator
Divide functional threshold or peak watts by body weight in kilograms. The result is W/kg.
Performance and e-bikes
Climbing VAM Calculator
VAM is elevation gained per hour. With body weight it also gives the power that lifts your body, the floor under your real climbing watts.
Performance and e-bikes
Speed to Watts Calculator
Estimate steady-state watts from speed, drag area (CdA), weight, rolling resistance and gradient.
Performance and e-bikes
Calories and Carbs Calculator
Estimate kilocalories from average watts and duration, and a carbohydrate target in grams per hour.
Performance and e-bikes
Cost per Gram Calculator
Divide the price difference by the grams saved. At 5 per gram or less, in any currency, the flag says the upgrade is in a sane range.
Performance and e-bikes
Bicycle Torque Guide
Common bicycle bolt torques in newton-metres for stems, seatposts, rotors, cranks, pedals and thru-axles.
Topics
- Bike fit and geometryFrame size, saddle, bars, stem and cleats.
- Drivetrain and gearingRatios, rollout, chain length and cassette range.
- Wheels and tiresPressure, spokes, sealant, ETRTO and circumference.
- Suspension and MTB setupSag, coil rate, rotors and flip chips.
- Performance and e-bikesW/kg, VAM, drag, range, fueling and torque.