Find the right bike size without the guesswork
Start with your height and inseam. BikeSize turns those measurements into a practical frame-size range, then points you to the brand chart or comparison that confirms the fit.
Only know height?
Start with Bike Finder, then add inseam when you have it.
Between sizes?
Use the result as a range, then confirm standover and reach.
Buying for a kid?
Wheel size, braking control, and confidence matter first.
What your result gives you
Road
inseam x 0.67
cm frame estimate
MTB
inseam x 0.66
converted to inches
Kids
wheel first
height + control check
Bike calculators for every fit question
Choose a quick starting tool below, or browse all 34 free calculators for sizing, fit, drivetrain, tires, and performance.
Measure once, get the first answer
The general bike size calculator turns height and inseam into a road, mountain, and hybrid starting size. Use it when you are not sure which tool to open.
Find my sizeAlready know the bike type?
Skip straight to the fit check that matches the frame you are shopping for.
Not every rider fits the average chart
Height and inseam get you close. Body proportions, confidence, and riding style decide which size actually feels right.
Browse all rider guidesCheck the bike you are actually considering
A calculator gets you close. Brand charts and head-to-head geometry show whether that specific frame will suit your body and riding.
Brand charts vary
Two brands can recommend different sizes for the same rider. Check the maker's chart before you order.
Compare reach, stack, use
If two bikes both fit on paper, compare geometry before you decide which one will feel stable, stretched, or upright.
Learn the fit basics once
Quick-reference sizing chart for every bike type — find your frame size by height in one glance.
Read guideWhen the number is not enough
Use these reads when the calculator result needs context: rider confidence, tall or short proportions, saddle comfort, and MTB fit.
Gear we would put on the bench first
Helmets, lights, locks, and hydration are the purchases that most often change safety or comfort. Start here before browsing every accessory category.
Safety first
Helmet, light, and lock are the first upgrades for most riders.
Fit still matters
Saddles, pedals, and bags should match your body and ride length.
Buy fewer things
Start with essentials that solve a real comfort or safety problem.
The shortlist
Four practical picks across the essentials. Each one earns its place before a rider buys nice-to-have kit.
Giro
Giro Register MIPS
S 51-55 cm, M 55-59 cm, L 59-63 cm
Niterider
Niterider Lumina Micro 950
950 lm: excellent for unlit roads and trails; 24-hour Femto mode for commuting.
Kryptonite
Kryptonite Evolution Series 4 Standard
Inner dimensions: 4" x 9" (10 x 23cm). Fits frame + single wheel through U + around fixed object. Standard commute size.
Camelbak
CamelBak Podium Chill 21oz
Standard 73mm bottle diameter. Optimized cage fit for most bike bottle cages.
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How to get a bike-size answer you can trust
Use the calculator for a starting range, then check the exact bike before you buy. These four checks show where the recommendation comes from.
Measure height and inseam first
Measure barefoot against a wall. Use a book or level to simulate saddle pressure for inseam, then recheck unexpected results before changing units or rounding.
Pick the calculator that matches the bike
Road, mountain, gravel, hybrid, BMX, and kids bikes use different sizing systems. If you are unsure, start with Bike Finder; otherwise choose the calculator for your bike type.
Confirm the result against the current brand chart
A medium in one brand may overlap a small or large in another. Check the current model's chart, then compare height range, stack, and reach when sizes overlap.
Use a test ride to settle close calls
Check standover, reach, control position, and your normal riding posture. For pain, numbness, injury history, or unusual proportions, see a qualified fitter or healthcare professional.
Take one measurement, then choose with confidence
Start with Bike Finder. Bring the result to brand charts, comparisons, and fit guides when you need the next check.
Sizing for every bike
Road, MTB, gravel, kids, e-bike, BMX, triathlon - all here.
No signup, no email gate
Free calculators, no funnel. Use as much as you want.
Backed by guides
Plain guides explain the why behind every number.