The Grow Tent Sizer. First-time growers almost universally over-buy tent space or under-buy light and ventilation — and neither mistake is cheap to fix. Run the tent sizer with the number of plants you actually want to grow and the training method you'll realistically do, and it'll tell you the tent, the light wattage, and the fan CFM in one pass. After the grow is set up, VPD and PPM/EC become the daily-use tools.

Both, with different assumptions baked in. The Grow Tent Sizer has a plant-type input that changes the plants-per-square-foot math — autos get higher density, photoperiods get lower. VPD and PPM/EC don't differentiate because the targets are roughly the same across cannabis genetics — your strain's indica-sativa balance shifts things more than auto-vs-photo does. Where plant type matters, the tool asks. Where it doesn't, we don't clutter the interface.

Partially. PPM/EC applies to outdoor grows in soil or hydro. VPD applies less directly because outdoor climate isn't something you control — you adjust to it, not set it. Tent sizer is indoor-only by design. Outdoor-specific tools (light hours by latitude, rain shelter sizing, pest pressure by region) aren't yet in the suite but are on the roadmap. If you're growing outdoors, the Learning Center's general cultivation guides apply fully; the calculators less so.

EC/PPM yes, VPD no. EC in coco runs about 20% higher than soil to deliver the same root-zone concentration because coco has less cation exchange capacity. Hydro runs similar to coco but drifts faster, so measure more often. Living soil can't be measured accurately on an EC meter at all — the biology controls availability, not bulk EC. Where it matters, tool copy notes the media adjustment. The PPM/EC converter treats EC as input or output; what feed chart you apply to it is where medium comes in.

Because VPD is the single measurement that tells you whether your plants can actually use the light, water, and nutrients you're giving them. Temperature and humidity in isolation are incomplete — a room at 78°F and 55% RH might be perfect for veg or disastrous for flower depending on how those two numbers combine. VPD is the combination. Dial it in and most deficiency, burn, and stretch problems disappear. Ignore it and no amount of perfect feed strength will compensate.

In development. Yield estimation is trickier than most tools in the suite because it depends on strain genetics, specific wattage per sq ft, container size, training method, and grower skill. The plan is to ship it as a probabilistic calculator ("expect 1.2–1.8 oz per plant based on inputs") rather than a precise number. Harvest Window Planner is simpler — it uses trichome maturity and pistil behavior — and ships sooner. Watch the Post-Harvest stage card above for status.