Erg-to-Boat Speed Predictor
Predict your on-water boat speed from erg scores using weight-adjusted power models and boat class factors.
Erg & Athlete Data
Solo sculling boat
Predicted 1x Speed
1:45.6/500m
17.0 km/h | 7:02.3 over 2000m
Erg Power
Weight Adj. Factor
Boat Speed
Predicted Speed Across All Boat Types
| Boat | Type | Split /500m | 2000m Time | km/h |
|---|---|---|---|---|
| 1x | Single Scull | 1:45.6 | 7:02.3 | 17.0 |
| 2x | Double Scull | 1:37.8 | 6:31.0 | 18.4 |
| 2- | Pair | 1:39.6 | 6:38.4 | 18.1 |
| 4x | Quad Scull | 1:31.0 | 6:04.1 | 19.8 |
| 4- | Four | 1:32.6 | 6:10.4 | 19.4 |
| 4+ | Coxed Four | 1:35.1 | 6:20.5 | 18.9 |
| 8+ | Eight | 1:25.8 | 5:43.3 | 21.0 |
| LM1x | LW Single | 1:50.0 | 7:19.9 | 16.4 |
| LM2x | LW Double | 1:42.5 | 6:50.0 | 17.6 |
Speed by Boat Class
Why Erg Speed Does Not Equal Boat Speed
A fast erg score does not automatically mean a fast boat. On the ergometer, body weight has a positive correlation with performance—heavier athletes can generate more absolute power. On water, that same body weight creates additional drag, especially in smaller boats like the single scull.
Research by Klusiewicz et al. found that the optimal allometric model for predicting single-scull performance uses the formula:
Adjusted speed = erg speed × mass−0.222
For aerobic distances (≥ 2000m). For sprint distances, the exponent increases to ~0.333.
This means two rowers with identical erg splits but different body weights will have meaningfully different on-water speeds. An 80 kg rower pulling 1:45 will likely be faster on water than a 100 kg rower pulling the same split.
Boat Class Speed Factors
Multi-person boats are faster than singles because power scales linearly with crew size while drag increases at a lower rate. The speed factors used in this calculator are derived from empirical data:
| Boat | Speed Factor | Notes |
|---|---|---|
| 1x | 1.00 | Baseline |
| 2x | 1.08 | ~8% faster than 1x |
| 2- | 1.06 | Sweep slightly slower than scull |
| 4x | 1.16 | ~16% faster than 1x |
| 4- | 1.14 | Four sweep, no cox |
| 4+ | 1.11 | Cox adds ~15-20 kg dead weight |
| 8+ | 1.23 | Fastest boat class |
| LM1x | 0.96 | Lightweight single |
| LM2x | 1.03 | Lightweight double |
What This Tool Cannot Predict
- Weather — headwind, crosswind, and tailwind significantly affect speed
- Water conditions — flat water vs choppy conditions, current, and water temperature
- Technique — on-water rowing skill differs from erg fitness
- Crew synchronization — in multi-person boats, timing is critical
- Rigging and equipment — boat setup affects drag and power transfer
Related Tools
- Boat Class Comparator — compare performance across boat classes
- Weight-Adjusted Score — Concept2 weight adjustment formula
- Race Pace Calculator — plan erg race splits
References
- BioRow: On-Water Speed Prediction — mathematical model based on thousands of measurements
- Klusiewicz et al. “Modelling the determinants of 2000m rowing ergometer performance” — allometric exponent research (0.222 for aerobic distances)
- Concept2 Forum: Scaling to OTW — community discussion on erg-to-water conversion methods