Nine calculators built on formulas that already have a name: the MET method for calories, Riegel's formula for predicting a new distance, Karvonen or the Cooper test for heart rate and VO2 max. Pick a tool, get a number you can check by hand.
Nine tools, each built for one specific number.
Calorie burn runs on the MET method behind the published Compendium of Physical Activities. The Race Time Predictor uses Riegel's 1977 exponential formula. Heart-rate and VO2 max tools use the Karvonen method and the Cooper 12-minute test, not a house shortcut invented for this site.
The Marathon Pace Calculator generates a checkpoint-by-checkpoint splits table with a print button built for race day, and several tools let you copy a shareable link with your own numbers already filled in, so you are not re-typing a pace goal from memory.
The marathon and half-marathon pace chart lists the required split for every common goal time at once, useful for comparing a few target paces side by side instead of running the calculator repeatedly.