About
About Zigzag Pulse
A small set of free calculators for heart rate training and common fitness tests, built to show their working.
What it is
Zigzag Pulse has five calculators: heart rate zones, target heart rate, VO₂max from the Cooper and Rockport tests, one-rep max and BMR and daily energy. Each one uses a published formula, shows the arithmetic under the result and lists its sources on the page, so you can check where every number comes from.
How it works
Everything is calculated by JavaScript in your browser. Nothing you type is sent to a server, and the calculators keep working if you go offline after the page has loaded. If you enter your age and heart rates on the zone or target page, they are kept in your browser's local storage so the other page can fill them in; the Reset button clears them. The privacy page has the details, including the cookie-free page-view counting the site uses.
What it is not
These are estimates from population formulas, and a real person can differ from them by a wide margin. Zigzag Pulse is not medical advice and is not a substitute for a fitness assessment or an exercise test. Talk to a doctor before starting intense exercise, particularly if you have a heart condition, take medicine that affects your heart rate or have been inactive for a long time.
The look
In light mode the pages are printed on ECG paper: 1 mm squares with heavier lines every 5 mm, and a red trace. Switch to the Monitor theme with the button at the top and the trace turns into a phosphor-green sweep on a bedside monitor. Both follow your system setting until you choose.