About PaceScope

PaceScope answers one question in two directions: what pace does a given finish time require, and what finish time does a given pace produce. It does that in five languages, and it publishes the formula behind every number it shows.

What it is

• A pace calculator and three distance charts — 5K, half marathon and marathon — with every finish time from a slow jog to a serious race, in both minutes per kilometre and minutes per mile.
• A VDOT calculator that back-calculates fitness from a race result and derives the five training pace ranges published by Jack Daniels.
• A race time predictor that converts one result into equivalent times at other distances using Riegel's formula.
• Five languages — English, German, Brazilian Portuguese, French and Spanish — with equal page sets in each. Not a machine-translated English site: every language has its own pages, and the terminology was chosen from measured search demand rather than from a dictionary.

What it is not

It is not a training service, a coaching product, or a health tool. There are no accounts and no stored results; the whole site is a single Go binary serving server-rendered pages. Google Analytics and Google AdSense are added at launch, with Google's consent management platform governing them — privacy states exactly what the server records and what those services set.

It also deliberately does not estimate maximum heart rate, heart rate zones, VO2max as a measurement, or Karvonen-style training intensities. Those are physiological claims with wide individual error bands, and the common 220 − age shortcut has a known systematic bias — guessing at them would be worse than leaving them out. The reasoning is on methodology.

How the numbers are kept honest

Three rules run through the whole site:

1. Formula or nothing. Every number comes from arithmetic (time ÷ distance) or from a named, published formula: the Daniels–Gilbert oxygen-cost equations for VDOT and training paces, and Riegel (1981) for predictions. Each is listed with its edition on sources.
2. Round once, at display. The site compares and stores exact milliseconds and rounds only the value it prints, so a pace is never compared against a rounded table. The rules are written out on methodology.
3. Say what is not known. Where a formula drifts — Riegel's exponent at ultramarathon distances, the difference between computed training paces and the printed tables — the page says so instead of implying precision it does not have.

Who it is for

Runners, and anyone else who needs to convert a time into a pace: someone checking whether a 4-hour marathon is realistic, someone building a training plan around a 20-minute 5K, someone translating a treadmill speed into minutes per kilometre. The pages are readable without JavaScript, printable, and addressable — every result is a link you can send to somebody.

Corrections

Found a wrong number, a bad translation or a formula we have misread? Please write to [email protected]. A correction with a source is worth more to us than a correction without one — see contact for what we can and cannot answer.