Welcome to the oldest and most popular bicycle performance prediction calculator on the web - since 1997. Effortlessly compute speed or power for all important parameters, such as weight, grade, position and tire type. This is actually an "engineering model" that knows the relationships between power, speed, and the three major forces: gravity, wind resistance and rolling resistance.
Our old friends will notice a big change here: the calculator on this page replaces four of the old calculators. You can enter your velocity to get your power, or vice versa. Or use the handy slider to change both at the same time (may not work with some browsers). You can choose metric or U.S. units.
You can also enter values for time, energy expenditure, or weight loss - your ride distance will be adjusted to match.
We're still working to get the kinks out. If you have any trouble or have suggestions, let me know: email@example.com. The old calculators are still around - see the "Old Stuff" menu item above.
Check out the iOS version of this calculator, and also our unique calorie-counting app - the easiest and fastest app of its type.
This will tell you what you need to know. Don't be flying blind! Sure, you could hang your iPhone on your handlebars, but remember: it's made out of glass and you can't be dripping sweat on it.
Ok, if you must, this is the best case for your double-sided glass phone.
Get warmed up for this year's tour by watching the best of last year's: a race where each and every stage was steeped in uncertainty and saw favorites' hopes raised and dashed and raised again. This is the 12hr Collector's Edition.