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
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.
The sweet spot for healthy vegetative growth in most crops.
Humidity too high or low for your stage? That's a ventilation or humidification 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 volume 2.9 m³.
A guide, not gospel — long duct runs, bends and summer heat load shift the answer. Bring these numbers in and we'll match a quiet EC fan, filter and controller properly.
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 | Dehumidifier, 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.
The gear that moves these numbers.
Bring them in. We'll make sense of them.
Screenshot your calculator results and show us in store, or phone (08) 9356 7044. Diagnosing rooms is the part of the job we actually enjoy.