Transpiration Rate Calculator

Work out transpiration rate instantly with clear inputs, formula shown and shareable results.

About Transpiration Rate Calculator

Divides water loss by leaf area and time, and converts to the millimole per square metre per second units used in gas exchange physiology.

Formula

Transpiration rate

Rate = water lost / (leaf area x time); mmol/m2/s = (g/m2/h / 18.015) / 3600 x 1000

Worked example

With the default values below, Transpiration Rate Calculator returns Transpiration rate of 375.000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Water lostaccepts 0.001–10,000 g: 15 g
Leaf areaaccepts 0–100 m2: 0.02 m2
Durationaccepts 0.05–240 h: 2 h

Results

Transpiration rate: 375.000 g/m2/h
Transpiration rate: 5.7822 mmol/m2/s
Water lost per hour: 7.5000 g/h
Loss over a 12-hour day: 90.000 g

Step by step

1Values used
2Transpiration rate
3Transpiration rate= 375.000 g/m2/h
4Transpiration rate= 5.7822 mmol/m2/s
5Water lost per hour= 7.5000 g/h
6Loss over a 12-hour day= 90.000 g

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

What drives transpiration?

The vapour pressure deficit between leaf and air, modulated by stomatal conductance and boundary layer resistance.

Typical rates?

Around 1 to 5 mmol/m2/s in well-watered plants in daylight, falling to near zero when stomata close.