Home / Climate Lab

Free tools. Real numbers. Better rooms.

We'd rather you measure than guess. These are the same calculations we run over the counter every day — use them at home, then come in (or call) if the numbers don't make sense. No signup, nothing collected.

VPD Calculator Fan Sizing Tool Stage Targets

VPD Calculator

Vapour pressure deficit is the single number that ties temperature and humidity together — it describes how hard the air is pulling water out of your plants. Set your room's readings below.

Air temperature 25.0 °C

Relative humidity 60 %

Leaf temperature offset

Tip: an infrared thermometer reads leaf temperature directly — ask for one at the counter.

Leaf VPD 1.05 kPa VEGETATIVE

The sweet spot for healthy vegetative growth in most crops.

Humidity too high or low for your stage? That's a ventilation question — the fix lives here, or ask us.

Extraction Fan Sizing

Under-sized extraction is the most common mistake we see in Perth rooms — especially once summer hits. Enter your space and we'll estimate the airflow your exhaust fan needs to move.

Room length 1.2 m

Room width 1.2 m

Room height 2.0 m

Carbon filter?

Light type

Recommended airflow 120 m³/h 125 mm class

Room volume 2.9 m³.

A guide, not gospel — long duct runs, bends and summer heat load shift the answer. The gear that moves these numbers lives here, and the counter does the fine-tuning.

Reference

Environment targets by growth stage

Ballpark ranges for most leafy, herb and fruiting crops under LED. Individual cultivars vary — treat these as a starting grid, then watch the plants.

Stage	Air temp (lights on)	Humidity	Target VPD	Priority gear
Cuttings & seedlings	22–25 °C	70–80 %	0.4–0.8 kPa	Heat mat, dome, gentle light
Early vegetative	23–27 °C	60–70 %	0.8–1.1 kPa	Oscillating airflow, timer
Established veg	24–28 °C	55–65 %	1.0–1.3 kPa	Extraction sized to room
Fruiting / flowering	22–26 °C	45–55 %	1.2–1.5 kPa	Steady air exchange, controller
Final weeks	20–24 °C	40–50 %	1.3–1.6 kPa	Tight RH control, monitoring

Perth-specific note: our dry summers push VPD high (add humidity or cooling) and our winter nights drop temperatures fast (watch lights-off humidity spikes). Local advice matters — it's why the shop's still here after twenty years.

Put Numbers Into Practice