VPDLAB
Enter your air temperature, relative humidity, and optional leaf correction to compute Vapor Pressure Deficit (VPD) — VPD calculator, VPD chart, and VPD checker tools for growers and researchers. Quickly see air and leaf-corrected VPD and compare against ideal bands for seedlings, veg, and flower.
Units
Leaf Temp
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VPD (Air) kPa
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VPD (Leaf‑corrected) kPa
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Nearest Stage
Seedlings: 0.4–0.8 kPa • Veg: 0.8–1.2 kPa • Flower: 1.2–1.6 kPa
Chart Axes (adjust to your typical ranges)
Temp Min
Temp Max
RH Min (%)
RH Max (%)
VPD Stage Bands (customize thresholds)
Seedlings (min–max)
Veg (min–max)
Flower (min–max)
VPD Formulas
SVP(T) = 0.6108 × exp( (17.27 × T) / (T + 237.3) ) kPa — T in °C
VPDair = SVP(Tair) × (1 − RH%/100)
VPDleaf = SVP(Tleaf) − SVP(Tair) × (RH%/100)
(Use Leaf‑corrected for most accuracy; RH input is percent.)
Leaf-corrected VPD uses leaf temperature instead of air temperature for more accurate readings, especially under LED lights where leaves are often warmer than the surrounding air.
My VPD Log
Entries are stored locally in your browser. Use the same device and browser to view previous log entries.
Click anywhere on the chart to drop a marker • Hover to probe VPD
Move cursor over chart…
Ideal VPD Key
Seedlings0.4–0.8 kPa
Veg0.8–1.2 kPa
Flower1.2–1.6 kPa
Below Ideal< 0.4
Above Ideal> 1.6
VPD FAQ & Quick Tips
What is VPD? Vapor Pressure Deficit (VPD) measures the drying power of air relative to plant leaves and is vital for irrigation and climate control.
Quick tips: Use the VPD calculator to check conditions; enable leaf-corrected when leaves are warmer than air; keep seedlings ~0.4–0.8 kPa.
About VPDLab
VPDLab is a lightweight, browser-based VPD calculator and visualizer. It computes air and leaf‑corrected VPD, shows ideal bands for seedlings, veg, and flower, and lets you export results. Use it to quickly check environmental conditions, compare against target bands, and make informed climate or irrigation decisions.