Last updated 12 October 2026.
What you type stays on your device
Every calculation happens in your browser. The numbers, tire sizes and settings you enter are not sent to us or to anyone else, and they are never included in analytics.
Your browser’s local storage keeps your unit choices (US or metric, and any unit you picked in the Units panel) and your cookie choice, under keys that start with ct:. You can clear them at any time by clearing this site’s data in your browser. Light or dark mode follows your device setting and is not stored.
Google Analytics, only if you accept
We use Google Analytics 4 to see which calculators people use and which pages need work. It does not load at all until you click Accept on the cookie notice. If you click Reject, or do not answer, nothing is sent to Google.
If you accept, Google Analytics sets the cookies _ga and _ga_ZH2LV8W8P6 and receives: the pages you view (without anything after ? or # in the address), the page you came from, your browser and device type, your approximate location as Google works it out from your IP address, and a few actions: starting to use a calculator, copying a result or a link, and changing units. It never receives the numbers, sizes or anything else you type. In Google Analytics itself, ad personalization stays switched off; the ads on this site are covered under Advertising below.
You can change your mind at any time with Cookie settings (also in the footer of every page). Choosing Reject stops Analytics and deletes its cookies. Google handles this data under the Google Privacy Policy, and Google offers a browser add-on to opt out of Google Analytics on every site.
Cloudflare
RPMkit is hosted and delivered by Cloudflare. Cloudflare processes the technical details of each request (such as IP address, browser type and the page requested) to deliver the site and protect it from attacks. We also use Cloudflare Web Analytics, which counts page views without cookies and without tracking you across sites. See the Cloudflare Privacy Policy.
Advertising
This site shows ads served by Google AdSense. Google and its partners, as third-party vendors, use cookies to serve ads based on your previous visits to this site and to other websites. Google’s use of advertising cookies lets it and its partners show you ads based on your visits to this site and/or other sites on the internet.
You can opt out of personalized advertising in Google’s Ads Settings. You can also opt out of some third-party vendors’ use of cookies for personalized advertising at aboutads.info/choices. Google explains how it uses information from sites that show its ads on How Google uses information from sites or apps that use its services.
If you are in the European Economic Area, the United Kingdom or Switzerland, you are asked for consent before advertising cookies are used, and you can change your choice at any time. If you decline, you may still see ads, but they are not personalized.
The ads never use the numbers, tire sizes or anything else you type on this site.
Share links
When you use a calculator, the page address changes to include your inputs after a # sign, so you can copy the link and share it. Browsers do not send that part of a link to any server, and it is not sent to Google Analytics.
If you write to hello@rpmkit.com, we receive your email address and your message and use them only to reply. We do not add you to any list and do not share them.
Changes
If anything on this page changes, we will update it here and change the date at the top.