VPD calculator & chart for indoor growing
Free VPD calculator and chart for indoor growing. Calculate air and leaf VPD, compare A/B, download PDF or PNG and share your settings.
Inputs
- Air VPD
- 1.11 kPa
- Leaf VPD
- — kPa
Sent only with your enquiry. The original CSV is not attached.
Take your VPD chart with you
A clear A4 sheet with the air VPD chart, your inputs and results. Print it, download it or share the same calculation.
VPD chart for temperature and humidity
Rows show air temperature, columns show relative humidity and cells show air VPD in kPa. Colours compare values; they do not indicate recommended crop conditions.
Select a cell to use its temperature and humidity in the active scenario. · Scenario A
| °C / RH | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|
| 18 °C | ||||||
| 20 °C | ||||||
| 22 °C | ||||||
| 24 °C | ||||||
| 26 °C | ||||||
| 28 °C | ||||||
| 30 °C | ||||||
| 32 °C |
Saturation vapour pressure uses the Tetens equation over water between −20 and 60 °C. Leaf VPD requires measured leaf temperature. Table colours indicate air VPD magnitude only; they do not prescribe crop conditions.
How we calculate
eₛ(T) = 0.6108 × exp(17.27T / (T + 237.3)); VPDair = eₛ(Tair) × (1 − RH/100); VPDleaf = eₛ(Tleaf) − eₛ(Tair) × RH/100 [kPa]Method source ↗How to use it
Measure air temperature and relative humidity near the crop at the same time. Enter °C and % RH.
Add measured leaf temperature if available. Leave it blank to calculate air VPD only; a missing measurement is not zero.
Change one input or compare A and B. Download the result with its assumptions when you need a record.
Same room, cooler leaf
Load the worked example above: air at 24 °C, relative humidity at 65% and a leaf at 22 °C. The two results use the same room humidity.
- Air VPD
- 1.04 kPa
- Leaf VPD
- 0.7 kPa
Reading the result
The cooler leaf has a smaller vapour-pressure difference from the surrounding air. Compare measurements taken under the same lighting and sampling conditions. These numbers describe the example; they are not a universal crop target.
Use the toolCommon questions
Can I use air temperature as leaf temperature?
Only as an explicit assumption. To see a leaf-specific result, measure the leaf. Otherwise leave that field empty; the calculator still returns air VPD.
Does a green table cell mean the crop is safe?
No. Colours help compare the magnitude of air VPD. They do not assess crop stage, irrigation, airflow, sensor accuracy or plant health.
Need a technical review of your growing data?
Turn sensor exports into a clear report on measurement quality, climate patterns and the checks that matter next.