15'10" rider on a road bike
Inputs
Height70 in
Inseam33 in
TypeRoad
Result
Frame Size56 cm
33" × 2.54 = 83.8 cm. 83.8 × 0.67 = 56.2 cm frame.
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Bike Fit Calculator
Frame Size
56 cm
Saddle Height
74.0 cm
Stem
79 mm
Recommended Frame Size
56 cm
Road Bike
Saddle Height
74.0 cm
Stem Length
79 mm
Fit Details
Reach29.8 cm
Stack46.1 cm
What You'll Need
DURATECH 41 Pieces Bike Repair Tools, Complete Bike Tools Kit with Storage Box, Mountain Bike Maintenance Tools, for Mountain, Road, and Park Bicycle with Chain Riveter, Tire Levers, Crank Puller
$59.99
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Bicycle Repair Bag With Tire Pump, Portable Tool Kit for Camping Travel - Bike Glueless Patches, Maintenance Essentials All in One Safety Kit
$22.70
View on Amazon
DURATECH 31 Pieces Bicycle Tool Kit, Complete Bike Repair Kit with Storage Box, Mountain Bike Repair Tools, for Mountain, Road, and Park Bicycle with Chain Riveter, Tire Levers, Crank Puller
$39.99
View on AmazonDURATECH 41 Pieces Bike Repair Tools, Complete Bike Tools Kit with Storage Box, Mountain Bike Maintenance Tools, for Mountain, Road, and Park Bicycle with Chain Riveter, Tire Levers, Crank Puller
$59.99
View on AmazonBicycle Repair Bag With Tire Pump, Portable Tool Kit for Camping Travel - Bike Glueless Patches, Maintenance Essentials All in One Safety Kit
$22.70
View on AmazonDURATECH 31 Pieces Bicycle Tool Kit, Complete Bike Repair Kit with Storage Box, Mountain Bike Repair Tools, for Mountain, Road, and Park Bicycle with Chain Riveter, Tire Levers, Crank Puller
$39.99
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Price as of Jul 24, 2026. Product prices and availability are accurate as of the date indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
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Example Calculations
25'8" rider on MTB
Inputs
Height68 in
Inseam31 in
TypeMountain
Result
Frame Size46 cm
31" × 2.54 = 78.7 cm. 78.7 × 0.59 = 46.4 cm frame.
Frequently Asked Questions
QHow is bike frame size calculated?
Frame size is based on your inseam length multiplied by a factor that varies by bike type. Road bikes use a 0.67 factor (inseam in cm), while mountain bikes use 0.59 due to their different geometry.
- Road bike: inseam(cm) × 0.67
- Mountain bike: inseam(cm) × 0.59
- Hybrid: inseam(cm) × 0.63
- Gravel: similar to road but slightly smaller
| Inseam (in) | Road (cm) | MTB (cm) | Best Frame |
|---|---|---|---|
| 30" | 51 | 45 | Small |
| 33" | 56 | 50 | Medium |
| 36" | 61 | 54 | Large |
QHow do I measure saddle height?
Saddle height is measured from the center of the bottom bracket to the top of the saddle. The 0.883 inseam method (multiply your inseam by 0.883) gives a reliable starting point for road bikes.
- Road: inseam × 0.883
- MTB: inseam × 0.870 (slightly lower)
- Heel should barely touch pedal at bottom
- Fine-tune with 1–2mm adjustments
QWhat stem length do I need?
Stem length depends on your arm length relative to the frame reach. Most riders use 80–110mm stems. Too short feels twitchy; too long causes neck and back strain.
- Short stem (60–80mm): more upright, stable
- Medium stem (90–100mm): standard road position
- Long stem (110–130mm): aggressive, aero
- Adjust spacers before changing stem length
QShould I size up or down between sizes?
When between sizes, size down for aggressive riding and size up for comfort. A smaller frame with a longer stem is more responsive; a larger frame with shorter stem is more stable and comfortable.
- Aggressive riding: size down
- Comfort/touring: size up
- Short torso/long legs: size down
- Long torso/short legs: size up
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Last Updated: Jul 24, 2026
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.