Sizing
Wetsuit size finderYour size in every brand Shoe size converterUK, US, EU and cm Bike frame calculatorRoad, mountain and hybrid
Swimming
Wetsuit thickness guideWhat to wear by water temp CSS calculatorCritical Swim Speed and zones Swim pace converterPool to open water, m and yd
Running
Race pace plannerSplits for your goal time Race time predictor5K to marathon from one result Hill effort converterGrade-adjusted pace Heart rate zonesFive zones, %max or Karvonen

Terms of use

The plain version: everything here is free to use, the results are estimates to guide you, and the final call is always yours.

Last updated 7 July 2026.

Who we are

Orion Sport is a free collection of calculators and size finders for running, swimming and cycling, run from the United Kingdom. Using any tool on this site means you accept the terms below. If you do not agree with them, please do not use the site.

The tools give estimates, not advice

Every calculator and size guide here produces an estimate from the numbers you enter and from published formulas or manufacturer charts. Bodies, brands and race days vary, so a result is a well-informed starting point rather than a guarantee. Always check a manufacturer's own size chart and returns policy before you buy, and always listen to how your own body feels when you train.

Nothing on this site is medical, safety or professional advice. If you have a health condition, are new to hard exercise, or are planning to swim in open water, get proper guidance from a doctor, coach or qualified instructor first. You use these tools and act on their results at your own risk.

What you can and cannot do

You are welcome to use the tools for your own training and buying decisions, and to share links to any page. You may not copy the site's content, code or data to rebuild a competing tool, scrape it in bulk, or try to break, overload or interfere with how it runs.

Availability

The site is offered as it is. We work to keep it accurate and online, but we do not promise it will always be available, error free, or up to date, and we may change, add or remove tools at any time.

Links and any affiliate relationships

Some pages may link to other websites, including retailers. Those sites are outside our control and have their own terms and privacy policies. If a link is an affiliate link, meaning we may earn a small commission if you buy through it at no extra cost to you, that will be made clear on the page. A commission never changes the sizing logic or the recommendations a tool gives you.

Our responsibility to you

As far as the law allows, Orion Sport is not liable for any loss that comes from using the site or from relying on a result, including a wrong size, a missed goal time or a purchase that did not work out. Nothing in these terms limits any liability that cannot be limited by law.

Changes to these terms

We may update these terms from time to time. The date at the top shows when they last changed, and continuing to use the site after a change means you accept the new version.

Governing law

These terms are governed by the law of England and Wales, and any dispute will be handled by the courts of England and Wales.

More information

For how your data is handled, see our privacy policy.