Watts to Split Converter for Aotearoa
Type a watt figure in and read back the 500m split your PM5 will sit on. Type a split in and read back the watts. The arithmetic is the canonical Concept2 cubic relation, so the answer matches the monitor on the erg in front of you. Built for the moment a coach chalks "hold 280W" on the boatshed door at Karapiro and a Year 12 sculler wants to know what number to chase on the screen.
Watts and split on a Concept2: the conversion in one line
Concept2 ties the two together with a single cubic relation: watts = 2.80 / (split_in_seconds / 500)^3, or rearranged, split = 500 * (2.80 / watts)^(1/3). At common setpoints, 200W lines up with 2:00.5, 250W with 1:51.9, 300W with 1:45.3 and 400W with 1:35.7. Because the relation is cubic, every 10-second jump down the split column costs more power than the jump above it. Moving from 2:00 to 1:50 needs about 61 extra watts. Moving from 1:50 to 1:40 needs another 87.
Input
Masters social: 100-200W. Open club and NZURA squad: 250-350W. Rowing NZ shortlist: 400W and up.
Most squad pieces in Kiwi programmes sit between 1:30 (Rowing NZ contender) and 2:30 (first session of pre-Maadi base).
At this pace
- Calorie burn:
- 2k time:
- 5k time:
Reference table
Common watts and split pairings off the Concept2 cubic relation. Pin this for piece programming, coach-set wattage targets through the winter Karapiro block, and quick reads during Maadi trial week.
| Split | Watts | 2k time | kcal/hr |
|---|---|---|---|
Method behind the converter
The Concept2 cubic power relation
Every PM3, PM4 and PM5 monitor in an Aotearoa boatshed runs on the same equation: watts = 2.80 / (split_in_seconds / 500)^3. Flip it for split and you get split = 500 * (2.80 / watts)^(1/3). Both directions are exact arithmetic, not a regression curve. The watt figure the Concept2 ergometer shows mid-piece is the figure this relation produces, derived stroke-by-stroke from flywheel deceleration. For the wider view across split, watts, kilocalories per hour and projected finishing times at every test distance a Kiwi crew runs, the erg pace calculator covers it.
Why the watts gap grows as the split shrinks
Power scales with the cube of pace. Halve the split and the watts requirement multiplies by eight. Run it the other way and doubling your power only shaves about 21 percent off the split. That is the reason 1:30 instead of 1:40 hurts so much more than 1:40 instead of 1:50, even though both are the same 10-second gap on the column. A coach setting watt targets without sanity-checking the matching split is one of the easier ways to write a piece that turns out twice as brutal as planned.
When the converter actually earns its keep
Three typical moments. First, the Karapiro coach calls a piece in watts and you need the split to hold on the monitor. Second, you are programming watt-pegged intervals into the squad practice record where members at different fitness bands need a single shared target. Third, you are scoring stroke-by-stroke max-power tests (10-stroke pulls, 1-minute pieces, standing-start work) where watts carries more meaning than the split column ever does. For mapping a 2k split out across the five intensity bands a Kiwi programme runs, the training pace calculator is the next stop.
Tracking watts across a Maadi build, not one piece on one erg
Converting a single watt figure is calculator work. Tracking thirty Year 11 to Year 13 athletes through a Karapiro winter block, a pre-Maadi camp at Lake Ruataniwha and the run-in to NZ Secondary Schools week is a database problem. Row HQ records every erg piece against the right athlete the moment the PM5 stops, so the head coach pulls crew lineups from live power data, catches a sculler quietly going backwards through the admin dashboard, and stops trawling Messenger threads to find last fortnight's PB. The Oundle Town RC case study shows the working pattern. The honest alternative is the shared-spreadsheet routine most boatsheds across Aotearoa are still running.
Frequently asked questions
Does this match what the PM5 actually shows?
Yes, to the figure. Concept2 publishes the formula and every PM3, PM4 and PM5 runs it unmodified. The watt reading on screen comes from flywheel deceleration measured stroke-by-stroke, fed straight through this relation. The only thing that changes the feel of a given wattage is drag factor, and drag factor does not alter the watts-to-split mapping itself. The numbers on this tool reconcile with the numbers on the erg in front of you.
Why does putting twice the watts in not cut the split in half?
Because the relation is cubic. To halve the split you would need eight times the watts, not two. Going the other direction, doubling watts trims about 21 percent off the split. The implication for training is the bottom of the curve is exponentially harder to move. Pulling 1:30 instead of 1:40 takes roughly twice the additional power that pulling 1:50 instead of 2:00 did. Coaches building piece progressions need to plan around that or the late-block sessions land much harder than the plan suggested.
What watts does a sub-7 minute 2k take?
A 7:00 2k holds a 1:45 split, which needs about 302 watts. Going under seven minutes needs more than 302 watts on average. A 6:30 needs about 378 watts, while a 6:00 needs about 480. Body weight and drag factor do not change this conversion.
Does changing drag factor change the conversion?
No. The coefficient (2.80) is fixed at every drag setting. Drag factor changes how the load feels and the rate you settle into, but it does not change the relation between watts and split. A 250-watt average produces a 1:51.9 split at drag 110, drag 125 or drag 140. Pick the drag setting that suits your weight and the goal of the piece.
Why is the watts readout so jumpy during a steady piece?
Because the monitor calculates watts per stroke from flywheel deceleration. Any small change in how you apply the drive shows up immediately as a visible swing on the watts readout, even when your split-by-stroke is smooth. Most Kiwi club and university rowers use split for pacing long steady-state work, where the rolling average smooths the noise, and switch to watts for max-power assessments where the stroke-by-stroke figure is what you actually want to read.
How does kcal/hr relate to the watts figure?
Concept2 derives the per-hour kilocalorie estimate as kcal/hr = (watts * 4) + 300. The flat 300 stands in for basal metabolism during exercise. So 200 watts works out to roughly 1100 kcal/hr, and 300 watts lands at about 1500 kcal/hr. Real-world burn varies with body mass, metabolism and boatshed temperature, but the figure is stable enough across sessions to use as a training-load proxy when planning fuelling through a heavy Karapiro winter camp.
More tools in the Aotearoa erg suite
Erg Pace Calculator
Drop a split in and pull back watts, kcal/hr and projected 2k, 5k, 6k, 10k finishing times.
Drag Factor Calculator
Dial in a drag-factor setting that matches your weight, training history and the piece on the whiteboard.
Stroke Rate Calculator
Work out distance per stroke from rate and split, or back-solve either side.
Bodyweight-Adjusted Erg Score
Compare lightweight and openweight 2k times on a single fair scale.
One watt figure is a calculator. A whole squad through Maadi is Row HQ.
Row HQ writes every erg piece against the right athlete automatically. Coaches across Aotearoa watch power trends roll up through the season instead of chasing scores through WhatsApp.