Race Effort Estimator

ITRA km-effort is the International Trail Running Association's standardised effort unit for trail races. The official ITRA formula uses gain only: km-effort = distance + gain/100. TrailMath extends this by adding descent cost (+ loss/200, a published convention of the TM1 model), because steep descents cause real eccentric muscle damage (Minetti, 2002) that the gain-only formula ignores. A race with 100km and 6,000m of gain/loss has a TrailMath effort-km of 190 - equivalent in effort to running 190km flat.

The estimated UTMB Index (0-1000) shown here comes from a log-linear model of score against flat-equivalent speed and course size, fitted to results read from public utmb.world runner profiles. It is reported as a range rather than a single number because the calibration is approximate. This is useful for comparing yourself across different races over time, but is not your official ITRA Performance Index or UTMB Index - both of those use proprietary formulas.

Your official ITRA Performance Index is a weighted average of up to your 5 best race scores over the past 36 months, computed by ITRA from your finish time against the course - not from your finish position. Estimate one here, or look yours up at itra.run (opens in a new tab). For how both scores are calculated and what counts as a good one, see the ITRA and UTMB index guide.

UTMB Running Stones are awarded for finishing a designated UTMB World Series race, by race category rather than by km-effort: Events give 1/2/3/4 stones for a 20K/50K/100K/100M, and Majors double it. See how qualifying actually works, or the official rules at utmb.world (opens in a new tab).

ITRA. Performance Index methodology. itra.run/FAQ/PerformanceIndex UTMB World. Running Stones rules. utmb.world/sports-system