We built millimeters.to because every other unit converter on the internet is fighting you. Popups asking if you want their newsletter. Ads stacked three high before you can see the answer. Cookie banners the size of a small country. You came to find out how many cups are in a liter, not to negotiate with seventeen tracking partners.
So this is the alternative. Type a number. See the answer. The end.
The problem we’re solving
Search “cm to inches” and look at what comes up. The top results are usually one of two things. Either it’s a calculator wrapped in so much aggressive monetization that you can barely find the input field, or it’s a thin auto-generated page that was clearly built by feeding a list of unit pairs through a template. The math is usually right, but everything around the math is hostile.
The frustrating part is that unit conversion is the simplest possible kind of utility. The formulas have been settled for centuries. There’s no reason the experience should be this bad. We think the real problem is that these sites were built for advertisers first and users second — every design decision optimized for time-on-site and ad impressions, with the actual conversion treated as the bait.
We took the opposite approach. The calculator is the page. Everything else — the formula, the reference table, the comparison diagram — exists to make the answer more useful or easier to understand. There are no email captures, no “read more” expansions, no autoplay videos, no chat bubbles pretending to be a person.
What you’ll find here
Conversions across length, weight, temperature, volume, area, speed, cooking, and trade measurements. The site currently covers about 150 conversion pairs, with more added regularly. Every page has:
- A live calculator that handles plain numbers, decimal values, fractions like
2 1/2, and imperial heights like5'10". You can type or paste, and the answer updates as you go. - The conversion formula in plain text, so you can do the math yourself or use it elsewhere.
- A reference table for the most common values, useful when you need quick lookup without typing.
- A visual comparison diagram that shows the actual size relationship between the two units. If you’ve ever wondered whether a centimeter is closer to an inch or to a foot, the diagram answers that in half a second.
- A short FAQ section answering the questions people actually ask about that conversion.
Every page also has structured data (schema.org markup) so search engines understand what it is. We do the unglamorous SEO work properly because we’d rather rank well than spam.
How we verify conversions
Standard SI and metric conversions are taken from the National Institute of Standards and Technology (NIST) in the United States and the International Bureau of Weights and Measures (BIPM) in France. These are the official sources for what a meter, kilogram, and second actually are, defined in terms of fundamental physical constants.
Imperial conversions reference the National Physical Laboratory (NPL) in the UK and the relevant ISO standards. The pound is defined as exactly 0.45359237 kilograms; the inch is defined as exactly 25.4 millimeters. These aren’t approximations — they’re exact legal definitions.
For cooking conversions involving ingredient density, we cross-reference data from established sources including King Arthur Baking’s ingredient weight chart, USDA food databases, and traditional culinary references like The Joy of Cooking and Modernist Cuisine. Where sources disagreed, we used the value most widely cited in professional baking — typically the King Arthur values, which are the de facto standard in American baking.
Trade and engineering conversions (drill bits, wire gauges, pipe threads) reference the relevant ASME, ANSI, and DIN standards.
When a conversion appears on the site, we’ve checked it against at least one authoritative source. If we ever cite a less common conversion where the answer depends on context (which version of the BTU, for example, or which gallon — US liquid, US dry, or imperial), we tell you on the page rather than silently picking one.
The data behind cooking conversions
This is the part most converters get wrong, so it’s worth explaining. When you convert “1 cup of flour to grams,” the answer isn’t a fixed number — it depends on which flour, how it was scooped, and whether it was sifted. A cup of all-purpose flour, scooped and leveled, weighs about 125 grams. A cup of bread flour weighs about 130 grams. A cup of cake flour weighs about 114 grams. Sifted flour weighs less than scooped flour from the same bag.
Most online converters skip this entirely. They treat “cup” as a fixed volume (236.6 mL) and convert volume to volume, which is technically correct but useless when you’re actually baking. Our cooking pages give weights for specific ingredients, using the values most professional bakers use, with a note about how the value was measured.
If you’re not a baker, this might seem like an obsessive detail. If you are a baker, you know that flour-by-volume is why so many home bread recipes turn out badly. Weighing ingredients is more accurate. We want our cooking pages to be useful enough that you actually use them in the kitchen.
How the site is built
The site runs on WordPress with a custom plugin we wrote ourselves. Each conversion is a database entry with the relevant data (units, conversion factor, category, notes), and the plugin renders the full page from that data using a single template. This means every page is structurally consistent, the formulas can be cross-checked in one place, and updates propagate everywhere at once.
We don’t scrape data from other converters. We don’t use AI to auto-generate page content. Every conversion was added deliberately, with the formula verified against the sources mentioned above. When we add a new conversion, it’s because we noticed someone asking for it — either in the contact form, in search trends, or because we needed it ourselves.
What we’re not
We’re not a venture-funded company pretending to be friendly. We’re not a content farm. We’re not affiliated with any measurement-related industry. We don’t sell anything except attention to advertisers (specifically Google AdSense, which is our only commercial relationship).
We’re also not infallible. If you find an error, tell us through the contact form — we fix verified errors promptly, and we list known issues at the top of any affected page until they’re fixed.
Who built this
millimeters.to is independently built and maintained by a small team. The site is in the process of being established as a Delaware limited liability company; until that’s complete, it operates under personal responsibility of its founder.
What’s coming
The current roadmap includes:
- Expanded cooking conversions for more ingredients (currently about 30 ingredients covered; aiming for 100).
- Specific-value pages like “150 cm in feet and inches” or “350°F to °C” — the exact queries people search for.
- More trade and maker conversions: tap sizes, screw thread pitches, pressure unit pairs.
- Dark mode because half the internet asked for one.
- Improved mobile experience with one-tap copy and a sticky calculator for long pages.
If you have a conversion that’s missing and you actually use, tell us, we’ll add it.