Endurance calculators

A small set of calculators for aerobic training and fuelling. Enter your numbers and the results update as you type; the address bar always holds the current calculation, so you can bookmark or share it.

Maffetone MAF heart rate

The 180 formula with all four health and training adjustments, plus the youth and 65-plus exceptions.

DIY sports drink

Turn a target carbohydrate and sodium concentration into grams of sugar and salt, with the osmolality it lands at.