Rowing Calculators

By the Watta Team · Updated

Sixteen free tools for indoor rowing, all built on the same Concept2 formulas the PM5 uses. Convert a /500m split to watts or back again, work out the pace a target time needs, predict a 2K from a 5K, adjust an erg score for body weight, or turn one benchmark into UT2, heart-rate and pace zones for every session in the week. Every tool prints a reference table of worked figures beneath it, so you can read the answer without touching an input. Nothing needs an account and nothing is stored.

Convert pace and power

The PM5 shows a /500m split; training plans and ergometer research talk in watts. These convert between the two using the Concept2 formula, so the same piece can be read either way.

Split Time to Watts ConverterConvert any /500m split to watts instantly using the Concept2 formula. See what a 2:00, 1:50 or 1:40 split is worth in power on the erg.Watts to Split Time ConverterConvert watts to a /500m split instantly. Find out what pace 150, 200, 250 or 300 watts equals on a Concept2 rowing machine.Rowing Pace CalculatorWork out the /500m split you need for any target time and distance — 2K, 5K, 10K or a half marathon — and see the watts it takes.Split Comparison ToolCompare two rowing splits side by side. See the difference in watts, total time over any distance, and the power cost of each second of pace improvement.

Predict a race time

Work out what a known result implies for another distance. All three use Paul’s Law, the rule of thumb that a doubling of distance costs roughly five seconds per 500m.

2K Time PredictorPredict your 2,000m erg time from a recent 5K, 6K, 1K or 500m result using Paul's Law — the rule of thumb rowers use to convert between distances.5K Time PredictorPredict your 5,000m rowing ergometer time from your 2K, 6K or another test distance using Paul's Law. Plan your 5K erg pacing.10K Erg Time PredictorPredict your 10K erg time from a known rowing distance result. Uses Paul's Law to estimate 10,000m performance from your 2K, 5K, or 6K time.

Compare scores fairly

A lighter rower moves less boat but also carries less flywheel advantage on the erg. These normalise a result so two people of different sizes can be compared.

Concept2 Weight Adjustment CalculatorGet your weight-adjusted erg time in seconds. Enter your time and body weight to see the Concept2 adjusted score and compare it fairly with anyone else.Rowing Power-to-Weight CalculatorCalculate your rowing power-to-weight ratio and weight-adjusted 2K time. Compare performance fairly across different body weights using the Concept2 adjustment exponent.Rowing Effort Score CalculatorCalculate your Watta Effort Score for any rowing workout. Combines cardiac load, work output, pacing, and economy into a single 0-100 score.

Set training intensity

Turn one benchmark into the paces and heart rates for every session in the week, rather than guessing at what "steady state" should feel like. If you only ever use one of these, make it the UT2 band: rowing easy days too hard is the most common way a training week quietly stops working.

Rowing Training Pace CalculatorCalculate your rowing training pace zones (UT2, UT1, AT, TR, AN) from your 2K erg time. Get personalised split targets for every type of training session.UT2 Pace CalculatorWork out your UT2 split, watts, stroke rate and target heart rate from a 2K time. A 7:00 2K puts steady state at 2:01.2–2:08.2 /500m at 18–22 spm.Rowing Heart Rate Zone CalculatorCalculate your five rowing heart rate zones using the Karvonen (heart rate reserve) method. Get personalised HR targets for UT2, UT1, threshold, and VO2 max training.Rowing VO2max EstimatorEstimate your VO2max from your 2K rowing erg time using the Concept2 formulas based on Fritz Hagerman's rowing research.

Energy and resistance

What a session actually costs, and what the damper is really setting.

Rowing Calorie Burn CalculatorHow many calories a rowing session burns, from your split, duration and body weight — the Concept2 monitor formula, corrected for your weight instead of the 175 lb default.Drag Factor CalculatorEstimate your Concept2 drag factor from damper setting. Understand the difference between damper and drag factor, and find the optimal setting for your training.

Split to watts at a glance

The conversion both converters run, at the paces most people train around. Computed with the same function the calculators call, so these figures and the tools can never disagree.

/500m splitWattsBack to split
1:40350 W1:40.0
1:45302 W1:45.0
1:50263 W1:50.0
1:55230 W1:55.0
2:00203 W1:59.9
2:10159 W2:10.1
2:20128 W2:19.8

Power scales with the cube of speed, so the watts gap between rows widens as the splits get faster. That is the whole reason a five-second improvement is worth celebrating at 1:45 and barely noticeable at 2:20.

Where the numbers come from

Pace and power use Concept2’s published constant of 2.8 (watts = 2.8 ÷ pace³, pace in seconds per metre). Calorie figures use the Concept2 formula, corrected for your body weight rather than the 175 lb default the monitor assumes. Weight adjustment uses Concept2’s 270 lb reference. Race predictions use Paul’s Law. Heart-rate zones use Karvonen from heart-rate reserve. Every tool names its method on its own page. Stats & Benchmarks has the reference tables if you want the numbers without the tool.

Frequently Asked Questions

What is a rowing calculator?
A rowing calculator converts between the numbers a Concept2 monitor shows and the numbers a training plan asks for. The monitor reports pace as a /500m split; plans are often written in watts, in percentages of a 2K, or in heart rate zones. Each tool here takes one figure you know and returns the one you need.
How do you convert a rowing split to watts?
Watts = 2.8 divided by the cube of the pace in seconds per metre. In practice that means a 2:00 split is 203 watts and a 1:40 split is 350 watts — power rises with the cube of speed, which is why taking four seconds off a split near the front of the range costs far more than four seconds near the back.
Are these the same formulas the Concept2 PM5 uses?
Yes. The pace-to-power conversion, the calorie formula and the weight adjustment all use Concept2’s published constants, so a figure here matches what the monitor or the online logbook would give you. Where a calculator uses something else — Paul’s Law for race predictions, Karvonen for heart rate zones — the page for that tool names the method.
Do I need an account to use them?
No. Every calculator runs in the browser, needs no sign-in, and stores nothing. The Watta app is separate: it logs your actual sessions from a photo of the monitor and scores them, but none of these tools require it.
What pace should I row steady state (UT2) at?
Between 55% and 65% of your 2K power, at 18–22 strokes per minute, with heart rate at 60–70% of heart-rate reserve. For a 7:00 2K that works out at roughly 2:01–2:08 per 500m. The UT2 pace calculator does the conversion from your own 2K and prints the band in splits, watts and bpm.
Which calculator should I start with?
If you have a recent 2K, start with the training pace calculator — it turns that one result into target splits for every training zone — or the UT2 pace calculator if you only want the steady-state band, which is where most of your week should sit. If you are trying to follow a watts-based plan on a monitor showing splits, start with the watts to split converter.
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