Terms of Use
Last reviewed 11 August 2026.
By using this site you accept the terms below. They are short because the site is simple.
What this site provides
Computed geometry and arithmetic derived from tire size codes and from figures you enter. Nothing more. The calculations are performed from published, standardised notation and from the standard load-index and speed-symbol series, using formulas set out on the methodology page.
What this site does not provide
No fitment verdict, express or implied. The site does not assess suitability, safety or road-legality for any vehicle, and no output of any calculator here may be read as approval to fit anything. Those assessments turn on the individual vehicle's clearance, its load requirements and the law where it is registered — none of which the site receives as input. Nothing here is professional, engineering, mechanical or legal advice, and no part of it should be treated as a substitute for the vehicle manufacturer's own documentation, the tire manufacturer's own specifications, or a qualified person looking at the actual vehicle. The scope of what is and is not answered is set out at what this site does and does not tell you.
Decisions about what to fit to a vehicle are yours. So are their consequences.
Accuracy
Every effort is made to keep the arithmetic correct and the source data honest. Geometric figures are computed rather than stored, and platform records state where their numbers came from and when they were last checked. Even so, published specifications change, model years differ, and a figure can be wrong. Figures are provided as they are, without warranty of any kind, and reliance on them is at your own risk. Corrections are welcome and are acted on.
Third-party services
Payments, the newsletter, the contact form, hosting, traffic measurement and — when it runs — advertising are operated by third parties, each named on the privacy page along with what it receives. Their own terms apply to the parts they operate.
Purchases
Paid material is delivered as a digital file by email. Because a digital file cannot be returned once sent, refunds are handled case by case — write to the contact address and explain the problem, and a reasonable answer will follow.
Content
The writing, the calculations and the drawings on this site belong to the site. Quoting a short passage with a link is fine and welcome. Republishing pages wholesale is not.
Product names, model names and manufacturer names appear here for identification only. No affiliation with or endorsement by any vehicle or tire manufacturer is claimed or implied.
Links
Some links to retailers may be affiliate links, which are described on the affiliate disclosure page. Links to other sites are not endorsements of what is on them.
Changes
These terms are updated when the site changes in a way that affects them. The date at the top says when that last happened. Continuing to use the site after a change means you accept the version then in force.
Governing approach
Nothing here is intended to exclude any liability that cannot lawfully be excluded where you live. Where a term would be unenforceable in your jurisdiction, that term applies to the fullest extent the law allows and the rest of these terms continue in force.