Concept2 Watts to Split Power Converter for Irish Crews
Drop in a wattage and the tool returns the 500m split that lands beside it on the PM5 monitor. Drop in a split and the watt number pops out the other side. Same canonical cubic relationship Concept2 prints on every flywheel, run instantly so an Irish coach's power target stops being an abstract figure halfway through an erg piece at Inniscarra, the Pres boathouse on the Lee or the upstairs gym at Skibbereen Rowing Club.
Concept2 power, plain English: watts in, split out
Concept2 ties the two numbers through one equation: watts = 2.80 / (split_in_seconds / 500)^3. Flip the equation and split = 500 * (2.80 / watts)^(1/3). At common setpoints, 200 watts is 2:00.5, 250 watts is 1:51.9, 300 watts is 1:45.3, 350 watts is 1:40.0 and 400 watts is 1:35.7. The cube on the denominator does the heavy lifting. Halving the split multiplies watt output by eight.
Input
Indicative bands across Irish programmes: social masters 100-200W, open-club and IURC squad 250-350W, Rowing Ireland shortlisted athletes routinely north of 400W.
Most squad-grade splits in an Irish boathouse sit between 1:25 (Rowing Ireland contender) and 2:30 (opening session of a novice trial block).
At this pace
- Calorie burn:
- 2k time:
- 5k time:
Quick lookup: common watts and split pairs
Canonical Concept2 figures pulled straight from the cubic formula. Print it out, stick it on the boathouse wall at Commercial, Garda RC or the National Rowing Centre, and stop solving the same arithmetic mid-piece.
| Split | Watts | 2k time | kcal/hr |
|---|---|---|---|
What the converter is doing under the hood
The one Concept2 equation that runs everything
Every Concept2 ergometer sold since the PM3 prints the same relationship on the flywheel: watts = 2.80 / (split_in_seconds / 500)^3. Rearranged for the split direction: split = 500 * (2.80 / watts)^(1/3). Neither side is a curve fit or a regression. Both reduce to one line of arithmetic, so the watt and split numbers on the PM5 at Inniscarra always reconcile to the screen in the Trinity gym and to the equation above. For a wider conversion across split, watts, calories and projected race-distance times, lean on the erg pace calculator.
Why halving the split number multiplies watts eight times
Pace and power sit on a cubic curve, not a straight line. Knock about 21% off the split number and watt output doubles. Halve the split and watts climbs eightfold. Moving from 1:40 to 1:30 needs about 130 extra watts. Moving from 1:50 to 1:40 needs about 87. Coaches should check the matching split before setting watt targets.
When an Irish crew actually reaches for the converter
Three live cases. Converting a coach-set wattage target into the split the PM5 monitor is going to display so the athlete actually knows what number to chase. Programming wattage-based intervals into the squad practice record when openweights and lightweights in the same session need matched relative loads. Stamping max-power pieces (a 10-stroke flying start, a 1-minute Wingate-style burst, a 250m hammer test) in watts because the average split is too noisy to compare cleanly. For the full split-to-zone breakdown across UT2, UT1, AT, TR and AN, the training pace calculator is the next stop.
Tracking watt progression across an Irish squad through winter
Running one conversion in your head is fine. Tracking how 30 athletes' watt outputs move through a winter erg block at the National Rowing Centre is a database problem. Row HQ writes every piece against the right athlete the moment it lands, so a coach pulls crew lineups from live power data, watches a Junior 18 quietly plateau on the admin dashboard weeks before the Castleconnell entry deadline, and stops trawling WhatsApp for a PB nobody quite remembers. Walk through the Oundle Town Rowing Club case study for how a working club turns watt history into selection calls, or weigh it against the shared spreadsheet workflow still running in most Irish boathouses.
Common questions on Concept2 power conversion
Is the Concept2 watts equation actually exact, or a rounded approximation?
Exact. Concept2 publishes the formula openly, and every PM3, PM4 and PM5 monitor in an Irish boathouse runs the equation without modification. The watt figure on the PM5 screen is computed from the flywheel's deceleration between drives, then mapped through the same 2.80 coefficient the equation uses. Drag factor changes how much air the wheel moves per stroke, and changes the feel of the load, but the watts-to-split relationship stays untouched.
Why does pulling twice the watts not give me half the split?
Because the relationship is cubic, not linear. Pace doubling (split halving) requires eight times the watts. Doubling watts the other way only drops the split number by about 21%. That is the structural reason the climb from 1:40 down to 1:30 in a Skibbereen erg trial costs disproportionately more energy than the climb from 2:00 down to 1:50. The bottom of the curve is exponentially harder, not a steady gradient.
What watt figure pairs with a sub-7-minute 2k in Rowing Ireland terms?
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 the drag factor on the flywheel shift the watt conversion?
It does not. The 2.80 coefficient is fixed across every drag setting. A 250-watt average is a 1:51.9 split at drag 110 or drag 140. Drag changes the feel of each stroke and the rate an athlete settles into, but the maths linking watts to split does not move.
Why does the watts number bounce around during a steady-state piece?
The PM5 computes watts on a per-stroke basis from flywheel deceleration. A small variation in drive force shows up immediately as a watt swing, even when the split-by-stroke is sitting flat. Most Irish crews settle on split for pacing during UT2 and UT1 work because it is the smoother metric, then switch to watts for short max-power efforts where stroke-to-stroke output is the actual unit of measurement.
How does the kcal/hr figure on the PM5 relate back to watt output?
Concept2 estimates it as kcal/hr = (watts * 4) + 300. The fixed 300 stands in for basal metabolic rate during exercise. So 200 watts reads roughly 1,100 kcal/hr on the screen and 300 watts reads roughly 1,500 kcal/hr. Real-world burn shifts with body mass, body composition and boathouse temperature, but the figure is repeatable enough across sessions to act as a relative training-load proxy when fuelling through a heavy winter block or the Irish Champs taper.
Companion tools in the Irish erg suite
Erg Pace Calculator
Convert any split into watts, calories and projected finishes across 2k, 5k, 6k and 10k.
Drag Factor Calculator
Settle on the drag factor that suits your bodyweight, training history and target piece.
Stroke Rate Calculator
Work out distance-per-stroke from rate and split, or solve the other direction.
Bodyweight-Adjusted Erg Score
Compare lightweight and openweight 2k scores on a fair age and weight scale.
One converter for the athlete. One Row HQ for the whole squad.
Row HQ writes every erg score, watt figure and split against the right athlete automatically, so an Irish coach watches power trends across the season instead of chasing PBs through WhatsApp threads and stale spreadsheets.