Erg 2k Predictor

One hard erg piece tells you more than a month of easy ones. Enter a time you have pulled, pick the distance, and this tool projects the rest of the board. You get a predicted 2k, 5k, 6k, 10k, half marathon and full marathon, each with the /500m split and the watts you would need to hold. Use it to set a target before you sit down on the rail.

How the prediction works

The math is the Riegel model, the same curve used for running race times. Take a known time T1 over distance D1 and the predicted time T2 over distance D2 is T1 times (D2 divided by D1) raised to the power 1.06. That exponent is what bends the line: pace fades as the piece gets longer, and 1.06 captures how fast it fades for a trained athlete.

A 7:00 2k feeds in as 420 seconds over 2000 m. For a 5k the tool computes 420 times (5000/2000) to the 1.06, which lands at 18:29. The same input gives you a 1:51/500m target split for that 5k and the watts that split represents.

Reading the split and watts

Every predicted row carries a /500m split and a wattage. The watts come from the Concept2 pace-power relationship: watts equal 2.80 divided by the cube of your split-per-500m in seconds. Halve your split and the power required goes up eightfold, which is why the last 250m of a 2k hurts the way it does. Pick the column you are racing, read the split, and tape it to the monitor.

Where it holds and where it drifts

Riegel is most honest within a few multiples of your test distance. A 2k predicts a 5k tightly. Stretch it to a marathon and the model runs optimistic, because pacing discipline, fueling and plain fatigue pull real splits slower than a clean power curve suggests. Test at the distance closest to your goal when you can, and treat the long rows as a ceiling to chase rather than a promise.

For a known watts or split conversion in the other direction, use the erg calculator. To build erg work into a wider plan that keeps your running and lifting moving too, read the hybrid athlete training guide.