Concept2 Watts and Split Converter
Two-way translator between watt output on the flywheel and the /500m split the PM5 monitor shows. Plug a coach-set wattage target into the box and it returns the pace you need to hold mid-piece. Feed it a split off a recent fall trial and it spits back the average watt figure that produced it. Built for varsity squads in Princeton, New Haven and Seattle who write workouts in watts rather than the boathouse next door who write them in pace.
Watts to /500m split on a Concept2 PM5: the working formula
Concept2 ties watt output to pace through a single line of arithmetic. Watts equal 2.80 divided by the cube of seconds-per-500 normalized by 500. Run that and 200 watts lands at 2:00.5, 250 watts at 1:51.9, 300 watts at 1:45.3 and 400 watts at 1:35.7. Rearranged the other way, split equals 500 multiplied by the cube root of (2.80 divided by watts). Both directions reduce to one equation, so the column on this tool matches the figure on your PM5 to the tenth. The cube term on the denominator is what punishes you on a 2k. Halve the pace number and watt output multiplies by eight.
Input
Indicative bands: masters social 100-200W, trained varsity 250-350W, IRA-grade openweight 400W and up.
Practice splits typically run from 1:30 (national team contender) out to 2:30 (first session of fall trials).
At this pace
- PM5 kcal/hr:
- 2k finish time:
- 5k finish time:
Watt and split lookup table
The pairs US programs reach for most often. Snapshot the page during winter base, or pin it next to the erg before a C.R.A.S.H.-B 2k.
| Split | Watts | 2k finish | kcal/hr |
|---|---|---|---|
Method behind the converter
The Concept2 cubic relation between watts and split
Every PM5 monitor in the country runs on one equation: watts = 2.80 / (split_seconds / 500)^3. Flip it for the inverse direction and you get split = 500 * (2.80 / watts)^(1/3). No regression, no fitted curve, no fudge factor. Watt readings on a Concept2 ergometer come straight from the flywheel deceleration between strokes, then through this formula. The numbers reconcile perfectly with what the monitor displays. If you need the wider conversion suite (split into watts, calorie rate and projected finishing times across every test distance), step over to the erg pace calculator.
Why doubling watts does not halve your split
The denominator is cubed. Doubling watt output drops the split number by roughly 21 percent, not 50. Moving from 2:00 to 1:50 needs about 61 extra watts. Moving from 1:50 to 1:40 needs another 87. Coaches who write practice in watts without checking the matching pace can make the hard end of a session much tougher than planned.
When this conversion actually earns its keep
Three concrete situations. First, taking a watt target a coach has called out at the top of practice and turning it into the pace you should hold on the monitor mid-piece. Second, programming watt-based intervals into the practice record when athletes pull at different weights and fitness bands, so a 280W instruction lands consistently rather than meaning four different splits across the squad. Third, benchmarking max-power efforts (a 10-stroke flyer, a one-minute open) where watts is the more honest unit because pace gets noisy over short windows. Once a 2k score is locked in, the pace and rate setpoints across every training band fall out of the training pace calculator.
Logging watt output across a full varsity roster
Running one conversion is a pocket-calculator job. Watching forty varsity, JV and novice rowers move their watt average across a fall block, a winter IRA build and the spring sprint season is a database problem. Row HQ writes every score against the right athlete the moment the screen finishes, so coaches pull lineups from current watt data, catch a sophomore quietly drifting backwards via the admin dashboard, and stop hunting PRs through GroupMe screenshots or last week's shared spreadsheet. Work through the Oundle Town RC case study for a working example, then set it next to the spreadsheet workflow most US programs are still running.
Common questions about Concept2 watts and split
Is the Concept2 watts-to-split formula exact, or an approximation?
Exact. Concept2 publishes the equation and every PM3, PM4 and PM5 monitor runs it without modification. The watt figure on the screen comes from flywheel deceleration between drive phases. Drag factor changes how much air the flywheel pushes per stroke, but the watt-to-pace relationship stays fixed. A 280 watt average is a 1:47.7 split on every PM5.
Why does adding 50 watts not shift my split by 50 watts worth of pace?
Because the relationship is cubic, not linear. Going from 200W to 250W cuts about 8.6 seconds from the split. Going from 350W to 400W cuts about 4.3 seconds. The pace target moves less as the watt target climbs, which is why small gains at the fast end demand so much more power.
What watt average should a US varsity 1V be holding for a sub-6:30 2k?
A 6:30 2k holds a 1:37.5 split, which needs about 378 watts. A 6:20 needs about 408 watts. A 6:00 needs about 480 watts. Body weight and drag factor do not change those conversions.
Does drag factor or damper setting change the watts-to-split conversion?
No. The coefficient (2.80) is constant across every drag setting from 100 to 220. Drag factor changes the feel of the load and the rate window that suits the athlete, but a 250 watt average is a 1:51.9 split at drag 110 or drag 140. Pick drag factor for your stroke and body weight, not to change the watt figure.
Why does the watt display swing around during a steady piece?
The PM5 calculates watts once per stroke from flywheel deceleration. A small variation in drive force lands as a visible watt swing even when split-by-stroke looks rock steady. Most US rowers anchor steady-state pacing on split (which the monitor smooths) and switch to watts during max-power tests or short flyers where stroke-by-stroke output is the metric that matters. Coaches scoring a flying 250m sprint at the start of fall trials will quote watts for the same reason.
How does kcal per hour on the PM5 relate to watts?
Concept2 ties them through kcal/hr = (watts * 4) + 300, where the 300 stands in for basal metabolism during exercise. So 200 watts is roughly 1,100 kcal/hr and 300 watts is roughly 1,500 kcal/hr. Actual calorie burn shifts with body mass and boathouse temperature, so the number is rough as a dietitian-grade figure. As a session-to-session training-load proxy it is consistent enough to plan a heavy IRA build week of fueling around.
Companion tools in the US ergometer suite
Concept2 Erg Pace Calculator
Drop a /500m split in and get watts, kcal/hr and projected finishing times across 2k, 5k, 6k and 10k.
Drag Factor Calculator
Pick the drag factor that suits your weight, event and stroke shape, not what you think looks impressive.
Stroke Rate Calculator
Calculate meters per stroke from rate and split, or back-solve the other way around.
Bodyweight-Adjusted Erg Score
Compare lightweight and openweight 2k times on a fair playing field for selection.
Tracking watt output across a forty-athlete varsity roster
Row HQ writes every piece against the right rower the moment it lands, so coaches read power trends straight off the dashboard rather than collecting them through GroupMe threads and shared spreadsheets.