Conservative component starting point
The calculator gives you a practical first direction without pretending crank length exists independently from your wider position.
Crank length calculator
Which crank length suits you?
Example measurements are filled in. Adjust them to your own measurements for a personal starting point.
1
Measure your inseam
Inseam
Barefoot, measure from the floor to the top of a book held firmly between your legs.
Optional. Only enter what you know about your own bike.
2
Choose your bike
Choose the category that matches your bike and intended use.
What this guidance does and does not tell you
This result helps you rule out unrealistic crank options. Saddle height, posture, and intended use still determine whether a change is actually worth making.
- Example starting point
- 172.5mm
A practical component starting point. Hip compression, pedaling feel and saddle height still need a separate check.
- 165mm
- 170mm
- 172.5recommendedmm
- 175mm
- 177.5mm
Recommended crank length: 172.5 mm
Check in this order
- Measure your inseam again before changing parts.
- Check saddle height and knee angle together with crank length.
- Test your position on a short ride before making further changes.
Free account
Make this advice more personal
See what a different crank means for your saddle height and gearing.
- Your details stay saved. No need to enter them again, even in other calculators.
- A narrower range. Your current crank length lets you compare it with a different crank.
- Your next step is ready. Take your inseam to the saddle-height calculator.
These details go with you to your account
Nothing entered yet. Move a slider or choose an option; only what you enter goes with you.
Save my details · free accountYour entered values go with you; there is no need to enter them again. No account? Your result above stays available.
Your entered details are only remembered for this browser session.
Example starting point172.5 mm
The short answer
The calculator selects an initial crank length from your inseam and bike type. Treat it as a starting point to compare with your current crank, not a requirement to buy a new component.
How we calculate
Your inseam in millimetres is looked up in the calculator's crank-length table. For some MTB results, the calculation selects a shorter crank for additional ground clearance.
What this cannot tell you
The table does not assess hip movement, pedal clearance or your preferences on your own bike. When changing crank length, also check saddle setup and component compatibility.
Worked example
An example with fixed inputs. Use the calculator for your own details.
Input
- Measured inseam
- 84.5 cm
- Bike type
- Road bike
Calculated result
- Crank length
- 172.5 mm
Common mistakes
- Entering height when the calculator asks for inseam.
- Treating a small difference from your current crank as proof that it is wrong.
- Failing to check the rest of your setup after changing cranks.
Practical component choice without fake certainty
This public calculator helps you narrow the choice before you make larger changes to your bike.
Built on inseam first
Inseam remains the most useful public input for ruling out implausible crank choices more quickly.
Helps narrow the choice
Use the result to compare available crank sizes before you replace parts.
Guidance
- Crank length should match inseam, bike category, and posture demands.
- Shorter is not automatically better. The right choice balances clearance, comfort, and pedaling feel.
- Use this together with saddle height and full fit targets rather than in isolation.
What's next?
Use this as a springboard, not the finish line
Create a free account to build your rider profile, start a personalized fit, and track future adjustments.
The calculator gives a practical starting point. An in-person fitter can add value for complex biomechanical issues.
FAQ
Does a shorter crank always improve comfort?
Not always. Crank length needs to match your inseam, bike category, and position goals rather than following a blanket rule.
Why is MTB crank guidance sometimes shorter?
MTB setups may favor slightly shorter cranks for pedal clearance and terrain control.
Explore more
Related tools and guides
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