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How to Measure Bike Tyre Size: A Practical Guide
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Time to read 3 min
Measuring your bike tyre may seem simple, but doing it accurately can save you from buying the wrong replacement or struggling with fit issues. Whether you're upgrading tyres or replacing a worn-out pair, this guide explains how to measure bike tyre size the right way—and what the numbers on your tyre really mean.
Bike Tyre Size Basics: Diameter × Width Explained
Bike tyre sizes are generally written as diameter × width. Before choosing new ones, you might want to consider using a precise inflator like the Woowind BP188 to pair the right size with reliable inflation.. For example, a standard mountain bike tyre might read 26×1.95 (inches), while a road bike might use 700×35C (French sizing) or 37-622 (ISO standard).
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Diameter: The outer height of the tyre when inflated.
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Width: The thickness of the tyre from side to side.
You might also see measurements in millimeters or inches, depending on region or brand.
How to Measure Tyre Diameter and Width Correctly
Step 1: Measure Diameter
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Use a tape measure to check the outer diameter of the fully inflated tire (in inches).
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Alternatively, for ISO sizing, measure from bead seat to bead seat in millimeters (e.g., 622mm).
Step 2: Measure Width
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Place a ruler or caliper across the widest part of the tyre.
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If you measure in inches, you can convert to mm by multiplying by 25.4.
Tip: Measure while the tyre is mounted and inflated for the most accurate reading.
Understanding Sidewall Size Markings
Tires almost always have size information printed on their sidewall. Here's how to decode them:
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Imperial format: 26×1.95 = 26 inches diameter, 1.95 inches wide
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French format: 700×35C = 700mm diameter, 35mm width
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ISO/ETRTO: 37-622 = 37mm wide, 622mm bead seat diameter
These numbers help match tyres to your rim and frame—always double-check before buying a replacement. If you're unsure how to handle installation, our guide on how to change a bicycle tyre can walk you through it.—always double-check before buying a replacement.
Why Tyre Size Matters for Fit and Performance
Choosing the wrong size can lead to:
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Frame rubbing if the tyre is too wide
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Handling issues with mismatched rim/tyre sizes
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Reduced comfort or traction if the width isn’t suited to your riding conditions
Always consider your riding surface, pressure range, and frame clearance when sizing up or down. After finding the right size, refer to our bike tire inflation guide to set the correct PSI.
Tips Before You Replace or Upgrade a Bike Tyre
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Take a photo of your existing tire's sidewall for reference
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Check your bike manual for compatible sizes
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Stick to the manufacturer’s recommended range
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Don’t assume all 700C or 26" tyres fit the same—width and bead seat diameter matter
Final Advice: Record, Measure, and Inflate With Precision
Measuring your bike tyre size correctly is the first step to a smoother, safer ride. is the first step to a smoother, safer ride. Whether you're commuting, trail riding, or cruising on weekends, having the right size ensures comfort, speed, and handling. After mounting your new tyre, use a precise pump to inflate to the recommended PSI to inflate to the recommended PSI.
FAQs
What is the easiest way to measure bike tyre size?
Check the sidewall for printed size codes like 26×1.95 or 700×35C. For more precision, measure diameter and width manually.
Can I use a different tyre size than what's listed?
Stick to the manufacturer’s recommendations. A wrong size can lead to fit issues, poor handling, or rubbing on the frame.
What does 700×35C mean?
It’s a French sizing format for road bikes: 700mm outer diameter and 35mm width. Equivalent ISO size is 37-622.
How do I convert tyre measurements between inches and millimeters?
Multiply inches by 25.4 to convert to mm. For example, 1.95 inches ≈ 50mm.
Do wider tyres offer more comfort?
Generally yes—wider tires absorb more vibration and provide better grip, but ensure your frame has enough clearance.
Accurate inflation and proper fit keep your ride worry-free. Record your ideal size, confirm compatibility, and enjoy the road ahead with confidence. Explore our electric air pump collection for versatile tools to keep every ride smooth.
Tim Huang
Tim Huang has extensive experience in the development and optimization of electric air pumps , specializing in portable tyre inflators, electric air pumps, and wireless inflation solutions . With a strong background in product development, procurement, and quality assurance , he ensures that every Woowind product meets high performance and reliability standards. Connect with Tim on LinkedIn: Tim Huang