Predict Boat 2k Time
from Crew Erg Scores
Type each rower’s 2k erg time, pick the boat class, and Boat Lift returns a predicted on-water 2k — using per-class erg-to-water transfer factors and a variance penalty for wide crew spread. Free, in-browser, no signup.
Quick answer
Boat Lift predicts a boat’s race time from per-seat erg power, body weight, and technique. Power-first model: boat_2k = avg_erg × mult + adj + variance − tech_bonus − consistency + weight_adj × 4 — then multiplied by the conditions factor (head ×1.05 · cross ×1.02 · flat 1.00 · tail ×0.97). Predictions for 1k / 2k / 5k. Accepts erg time (2k / 5k / 6k tests), watts, or 500m split. Outputs W/kg, Boat Lift Score, and Synergy alongside the boat time. Useful for seat racing, pre-regatta planning, and lineup comparisons.
Each rowing seat takes 4 inputs: Erg Time (M:SS.s), name, weight (kg), technique 1–10. Cox seats need a name only.
+ variance − tech_bonus − consistency
+ (avg_weight − 85) × 0.04 × 4
result = boat_2k × cond_mult
watts = 2.80 / (split / 500)³ (Concept2)
Erg-to-water transfer factors
The constants Boat Lift uses for each class. Larger boats with more crew amplify (multiplier < 1, negative adjustment); smaller boats — especially the single — attenuate.
| Boat Class | Multiplier | Adjustment | Effect at 6:30 avg erg |
|---|---|---|---|
| Eight (8+) | 0.91 | -8 | ~5:47 boat 2k |
| Coxed Four (4+) | 0.95 | -6 | ~6:04 boat 2k |
| Straight Four (4-) | 0.94 | -7 | ~6:00 boat 2k |
| Quad Sculls (4x) | 0.93 | -8 | ~5:55 boat 2k |
| Double Scull (2x) | 0.97 | -3 | ~6:18 boat 2k |
| Pair (2-) | 0.99 | 0 | ~6:26 boat 2k |
| Single Scull (1x) | 1.05 | +12 | ~6:55 boat 2k |
How it works
- Step 01
Pick boat class + conditions + race distance
Boat class (8+ through 1x). Conditions multiplier (flat × 1.00, headwind × 1.05, tailwind × 0.97, crosswind × 1.02). Race distance (1k / 2k / 5k) decides which prediction is the headline number — all three are computed every time.
- Step 02
Choose erg input mode
Enter erg data as a 2k full time, direct watts, or a 500m split. When using full time, also pick whether the test was a 2k, 5k, or 6k — the calculator normalizes longer tests to 2k-equivalent watts.
- Step 03
Fill the seat cards
Each rowing seat: erg input, optional rower name, body weight in kg, and a technique rating 1–10 (default 7 — neutral). Cox seats only need a name. Tab through fields or click any input directly.
- Step 04
Predict boat speed
Hit Predict Boat Speed. The calculator converts each seat to 2k-equivalent watts, derives a 2k erg time, then applies the boat-class transfer factor plus variance, technique, consistency, weight, and conditions adjustments.
- Step 05
Read the breakdown
The score panel shows the focused-distance time and split, all three race times, W/kg, the Boat Lift Score, and the Synergy number — plus a metric row per adjustment. The seat-breakdown table lists every rower's 2k erg, watts, weight, W/kg, technique, and personal score.
- Step 06
Iterate + save
Swap rowers, tweak technique ratings, save lineups, and compare. Saved lineups persist in your browser. The race-visualization track shows where each lineup would be when the leader crosses the line.
Frequently asked questions
What is the Boat Lift Calculator?
A free rowing tool that predicts a boat's race time from each rower's erg power, body weight, and technique rating. Inputs go through a power-first model: every seat is converted to 2k-equivalent watts, then to a 2k-equivalent split, then aggregated through boat-class transfer factors and adjustments for spread, technique consistency, body weight, and wind/water conditions.
Do I need to sign up to use it?
No. The calculator runs entirely in your browser, requires no account, and does not transmit any data. Saved lineups persist in localStorage on your device only.
What inputs does the calculator need?
Per crew: boat class, race conditions, race distance, erg input mode, and erg test (when entering full erg times). Per seat: erg data, optional rower name, body weight in kg, and a 1–10 technique rating. Cox seats only need a name.
What erg input modes are supported?
Three: 2k full erg time (M:SS.s for a 2k, 5k, or 6k test), direct watts, or 500m split. Whichever you pick, the calculator normalizes everyone to 2k-equivalent watts before computing the boat speed. Long-test entries (5k, 6k) are lifted to 2k power using empirical multipliers (5k → 2k watts ÷ 0.78, 6k → 2k watts ÷ 0.74).
How is body weight used?
Two ways. (1) The W/kg metric divides total crew watts by total crew weight — a key indicator of how much power each kilogram is producing. (2) The weight adjustment adds (avg_weight − 85) × 0.04 seconds per 500m, per kilogram above an 85 kg reference. A crew averaging 90 kg adds about 0.2s/500m, ~0.8s over a 2k. Heavier crews need more power to push the boat through the water.
What is the variance penalty?
When the spread between the fastest and slowest rower exceeds 8 seconds (in 2k-equivalent erg time), the calculator adds 0.4 seconds per second of spread over the threshold, capped at 8s total. Mismatched crews lose boat speed to coordination overhead.
What does the technique rating do?
Each rowing seat takes a 1–10 technique rating (default 7 — neutral baseline). Two effects flow from it. (1) Average technique drives a tech bonus of (avg_tech − 7) × 0.6 seconds. (2) Technique standard deviation drives a consistency bonus of max(0, 2 − std) seconds. A crew with all 7s shaves the full 2s; a mixed crew with high std shaves none. Rate technique by eye-test for catch sharpness, finish, and rhythm — independent of erg power.
How do race conditions affect the prediction?
Conditions are a multiplier on the predicted 2k boat time. Headwind: ×1.05 (5% slower). Crosswind: ×1.02 (2% slower). Flat water: ×1.00 (baseline). Tailwind: ×0.97 (3% faster). A 5% headwind hits a 5:50 boat by ~17.5s — much larger than a flat additive penalty would capture.
How do race distances differ?
The calculator predicts 1k / 2k / 5k from the same crew data. 1k pace is faster (×0.96 of 2k split — anaerobic). 5k pace is slower (×1.08 of 2k split — steady state). All three are surfaced after each calculation; the "race distance" selector simply chooses which one is highlighted.
What is the Boat Lift Score and Synergy number?
Two 0–100 composites that distill the prediction into a single label. Score = avgTech × 7 + W/kg × 8 + max(0, 5 − spread) × 1.5 − variance — rewards strong, well-matched, technically sound crews. Synergy = avgTech × 6 + consistency × 12 + max(0, 5 − spread) × 2 — rewards crews that move together, regardless of raw power.
What boat classes are supported?
Eight (8+), Coxed Four (4+), Straight Four (4-), Quad Sculls (4x), Double Scull (2x), Pair (2-), and Single Scull (1x). Each class has its own erg-to-water transfer constants empirically tuned to typical race results.
Can I use it for masters or junior crews?
Yes — the calculator is age-agnostic. Enter the rowers' actual erg data and weights and pick the right boat class. The transfer factors are constant; what changes is the input. The weight adjustment naturally handles lighter junior or heavier masters crews via the (avg_weight − 85) term.
How is this different from Speed Order™?
Boat Lift is a forward-looking lineup predictor — it answers "if I put these rowers in this boat, how fast will it go?" Speed Order™ is the historical performance rating computed from actual race results. Boat Lift uses erg + biometric data; Speed Order uses race finishes. Use Boat Lift for lineup planning, Speed Order for ranking.