Unit Converter
One engine, one page per pair. Type a number, copy the other side. No ads when a unit changes. The math stays in this tab.
The number stays in this tab
I built this because a converter I opened to turn 350 F into Celsius put a video in front of the answer. Changing the unit fired an ad. That is the named complaint about these apps, and it is a strange tax on a multiply.
This page does the multiply here. Open the network panel, type 10 centimeters, and you will not see 10 or 3.937 go out. Mixpanel and Google Analytics load with the rest of Softery.io. They see that someone opened the tool. They do not get the number. If you came here because a privacy page promised zero third-party scripts, that is not this site, and I will not write that sentence.
After the layout has loaded you can unplug the cable and still convert. There is no account and no upload. Refreshing keeps you on the same pair. The number itself is not stored.
One URL per pair people type
A generic converter with a category picker answers "unit converter". It does not answer "cm to inches". People add those words because the first result wasted their time. Each pair here has its own address, so the page they land on is already the conversion they asked for.
Both boxes update as you type. The pointer on a wheel is decoration around a pick that already happened. The same idea applies here. The result is a multiply, or an affine temperature map, and the animation is you watching the other box change.
Swap is a real link. It opens the reverse pair with the current answer filled in, so someone can send inches to cm after they started on cm to inches. Add ?v=10 to any pair if you want that number waiting when the page opens.
The inch is 2.54 cm, exactly
Length uses the international yard. One inch is 2.54 centimeters. One foot is 0.3048 meters. One mile is 1,609.344 meters. Weight uses the avoirdupois pound of 0.45359237 kilograms. Volume uses the US gallon of 3.785411784 liters, which is 231 cubic inches, and a US cup of 8 US fluid ounces.
Temperature is the odd one. Celsius to kelvin adds 273.15. Fahrenheit to Celsius is (F minus 32) times 5/9. 350 F is 176.667 C, which is the oven number that started this page. 32 F is 0 C. 212 F is 100 C. Minus 40 is the one point both scales share.
Height is split on purpose. 173 cm is 5.67651 feet as a decimal, and it is also 5 ft 8.11 in. The cm to feet and inches page prints the classroom form. The decimal page stays a straight multiply.
What this page will not do
It will not convert an imperial gallon unless you do the last step yourself. The gallon here is the US gallon. It will not convert a currency, and it will not fetch a live rate. Those belong on a different tool because they are not constants.
It will not scale a recipe by ingredient density. A cup of flour is not a cup of water, and that table is a later page. A US cup on this page is 8 fluid ounces, always.
I wrote up why the other converters put an ad on a unit change on the blog. Nearby: the word counter, the password generator, and the wheel spinner. Same habit. Do the useful bit in the tab.
Common questions
Do you show an ad when I change a unit?
No. Change the number, or follow the swap link to the reverse pair. Nothing sits between those two clicks. The page is free because the arithmetic costs nothing to run.
Does the number I type leave this tab?
The conversion runs in this tab. Mixpanel and Google Analytics load with Softery.io. They see that someone opened the tool. They do not get the number you typed.
Why is there a page per pair instead of one giant dropdown?
Because people type cm to inches, not unit converter. A dropdown of a thousand units answers a different question. Each pair here has its own address, its own chart and its own formula.
Which gallon and which ounce are these?
US gallon and US fluid ounce for volume, avoirdupois pound and ounce for weight. The inch is the international inch of 2.54 centimeters exactly. The page says so next to the formula.