Email is the reliable way to reach us:

hello@nxtolerance.com

We read every message. To get the fastest useful answer:

• Found a math error? Tell us the exact inputs (mode, distance, time or pace, units) and the answer you expected. Calculation corrections jump the queue ahead of everything else — a 50:00 10K should be 5:00/km and 8:02.8/mile, and if it ever isn’t, we want to know today.
• A split or prediction looked wrong? Include the mode and the numbers — especially which preset or custom distance you used, since “half” (21.0975 km) and custom 21 km produce legitimately different results.
• Have a feature request? Popular asks so far: age-graded performance scores, negative-split plan export, and per-lap track splits beyond 400 m. We keep a list and build the most useful ones first.
• Something broken on your device? The browser, device and a screenshot help more than a description alone.

We can’t coach you — training advice for your specific body, injury or race belongs to a qualified coach or clinician. For everything about the calculator itself, we answer.