All tools

Free, fast, no signup. Pick a calculator, get your number, go run.

Summer essential

Heat & Humidity Pace Calculator

How much should you slow down today? Enter temperature and humidity, get your adjusted pace — with the science behind it.

 Race day

Marathon Fueling Calculator

How many gels, and when? Get a printable minute-by-minute fueling schedule for your marathon or half.

 Training

Pace Percentage Calculator

Workout says "95% of 5K pace"? Get the exact split — or flip it to find the race pace a workout implies.

 Goal setting

Race Pace Calculator

Pick a distance and goal finish time, get the pace you need to hold — in miles and kilometers.

 Predictor

Race Time Predictor

Enter 2+ recent races and get predicted times fitted to your own fatigue factor — not a generic formula.

 Indoor

Treadmill Pace Converter

Turn the mph on the console into the pace in your plan — every speed from 3.0 to 12.9 mph.

 Race day

Printable Pace Band

Get a wrist-sized band of your goal splits — print it, tape it, wear it on race day.

New tools ship regularly — bookmark this page to catch them first.