Kilogram Exponent (KGE) is the value Xert uses to show how much rider weight matters for performance on a given terrain. Higher KGE = weight matters more (steeper climbing). Lower KGE = weight matters less (flatter or descending).
Definition
Kilogram Exponent (KGE) is the exponent used in Xert’s Relative Power calculations. It changes based on the gradient of the terrain.
A quick way to think about it:
- Steeper terrain → higher KGE → W/kg matters more
- Flatter terrain → lower KGE → raw watts matter more
What It Means
KGE helps Xert “blend” between watts and watts/kg:
- When KGE = 1, Relative Power behaves like Watts/kg
- When KGE = 0, Relative Power behaves like Watts
So as the road tilts up, body weight plays a bigger role; as it flattens out, weight matters less.
Why KGE Isn't Zero on Flat Ground
On flat terrain, gravity contributes nothing to resistance — so at first glance, weight shouldn't matter. But XRP still adjusts for weight on the flats, because heavier riders also carry more inferred rolling resistance and aerodynamic drag (heavier riders tend to have larger frontal areas).
These effects are built into the KGE curve at each gradient. On the flats, KGE is small but non-zero. As gradient increases, gravity dominates and KGE approaches 1 — meaning the weight penalty grows.
How Xert Uses It
KGE in Relative Power
Xert uses KGE to estimate what power a standard 75 kg rider would need to match your effort on that terrain.
Average KGE for an activity
Xert calculates an activity’s average KGE using a weighted average based on gradient and your power, so hard climbing influences KGE more than easy coasting downhill. ou’ll See It
- In Race AI / performance modeling contexts where Xert is accounting for terrain and rider weight using Relative Power.
Related Terms
- Relative Power
- Race AI
- Xert Equivalent Power (XEP)
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