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Helmet Size Calculator

Find your helmet size from your head circumference — for cycling, ski, skate and climbing helmets. A correctly sized helmet is what makes it protective.

🪖 Fit is a safety feature. A helmet that's too loose can't protect you in a crash. Measure your head circumference about 2.5 cm above your eyebrows, snug but not tight. Every brand's bands differ slightly, so measure first and check the specific chart — and if between sizes, size up and use the fit pads.

Find your helmet size

⚠️ Bands vary by brand and helmet type. Measure twice, check the specific helmet's chart, and make sure the fitted helmet sits level and doesn't rock or slide. Replace any helmet after an impact.

How to measure

  1. Wrap above the brows

    Put a soft tape around the largest part of your head, about 2.5 cm above the eyebrows and ears.

  2. Snug, not tight

    Keep the tape level all the way round; don't pull it into the hair.

  3. Match to the size

    Compare your cm measurement to the band — the calculator gives the standard size.

  4. Check the fit

    A good helmet sits level, doesn't rock side to side, and stays put when you shake your head before the strap is done up.

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★ Top pick · Recommended on Amazon
Cycling Helmet

Well-ventilated helmet with an adjustable cradle for a secure fit.

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Helmet Fit Pads

Spare padding to dial in the fit when you're between sizes.

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Soft Tape Measure

Measure head circumference accurately before choosing a size.

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How these sizes are calculated

Bike frame sizes are derived from inseam using the standard fit multipliers (road x0.70, hybrid x0.685, mountain x0.225 in inches), with a height band as a quick starting point. Helmet and glove sizes map a body circumference to size bands. These are starting points — geometry and fit vary by brand, so confirm before buying, and for safety gear like helmets, never ride in one that doesn't fit.

Sources: Bike fit formulas & height/inseam charts (Cyclists Hub, RoadBikeRider, Icebike, 2026); Helmet head-circumference bands cross-checked (evo, multiple manufacturers, 2026); Glove hand-circumference sizing (standard S/M/L/XL bands).