# Bike helmet sizes by head circumference Which bike helmet size fits a given head circumference? Banwood Eco Helmet: The Australian maker page says ages 3\+, head circumference 50–54 cm, and Australian/New Zealand Standards certified; the UK maker page gives ages 2–7 and 52–56 cm, so the age and size figures disagree\. The maker says the age range is only an estimate and the child’s head should be measured before ordering\. Banwood Classic Helmet: The XS size is 48–52 cm, approximate age 18 months to 4 years\. Straps should not cover the ears and the buckle should stay away from the jawbone\. ### 1. [Banwood Eco Helmet](/products/ucp/modernnursery-com/14733684736366) (sold by modernnursery\.com) The Australian maker page says ages 3\+, head circumference 50–54 cm, and Australian/New Zealand Standards certified; the UK maker page gives ages 2–7 and 52–56 cm, so the age and size figures disagree\. - Head size range: The Australian maker page says ages 3\+, head circumference 50–54 cm, and Australian/New Zealand Standards certified; the UK maker page gives ages 2–7 and 52–56 cm, so the age and size figures disagree\. (guide) - Measure first: The maker says the age range is only an estimate and the child’s head should be measured before ordering\. (guide) - Strap fit: - ### 2. [Banwood Classic Helmet](/products/ucp/modernnursery-com/6545851351140) (sold by modernnursery\.com) The XS size is 48–52 cm, approximate age 18 months to 4 years\. - Head size range: The XS size is 48–52 cm, approximate age 18 months to 4 years\. (guide) - Measure first: - - Strap fit: Straps should not cover the ears and the buckle should stay away from the jawbone\. (manual) Every value in the table is a fact RoboTrunk checked, linked to the page it came from\. A dash means no checked fact fills that cell\. Prices and stock change, so this page prints neither: each product name links to its RoboTrunk page, which shows them live\. Written 2026-10-26T21:41:46.921Z. This page is published by RoboTrunk, a store built for shopping agents. The store named on this page sells the product and ships it. RoboTrunk is not the seller and never holds the money. Buying works in one path. RoboTrunk's tools prepare a checkout at that store, then hand back a short-lived link. The person approves the total; once RoboTrunk has checked the store's total against it, the person is given the checkout link to tap in their own browser, or, if the person prefers and gives permission, their agent may open the link and finish there, and payment always happens on the store's own checkout page. RoboTrunk never takes the payment or sees a card. Where the rest of this site is: - /agent/story.md is what RoboTrunk is and how it works, in full. - /agent/tools.json is every tool, its arguments and its answers. - /agent/merchants is every store you can buy from through RoboTrunk. - /products/ucp is every store's indexed products. - /products/search is one search across every store, in plain words. - [What RoboTrunk is](/agent/story.md) - [Every tool, in your browser through WebMCP](/agent) - [The tools and how to call them](/agent/tools.json) - [The stores you can buy from](/agent/merchants) - [Every store's products](/products/ucp) - [Search every store at once](/products/search)