Veg-phase calculators for cannabis grows
Plant spacing, pot sizing, training timing, veg duration. The veg-phase decisions that determine the canopy you flower — and the yield you harvest. Get them right and flower stage falls into place; get them wrong and no amount of bloom feed compensates.
Cannabis veg-phase toolkit
Every veg-phase calculator in the cannabis suite. None are live yet — all currently in active build. Each tool will run with cannabis-specific genetics defaults (autos vs photos), pot sizing math tuned for cannabis root systems, and training windows calibrated for cannabis structural development.
Plant Spacing & Pot Sizer
Two answers in one calculation. Input your tent size and training method, get plants per sq ft and ideal pot size for each stage. Or input your plant count and get the tent footprint and pot sizes you need. Cannabis pot sizing follows roughly 2 gallons per foot of expected plant height.
Veg Duration Estimator
Estimate ideal veg time based on tent height, target yield, and strain genetics. Cannabis stretches 1.5–3× during flower; vegging too long means hitting the light, too short means underdeveloped canopy.
Training Timeline Planner
Schedule the best days to top, LST-tie, ScrOG-net, or supercrop based on your veg start date and target flip date. Training timing matters as much as technique — wrong timing damages plants instead of shaping them.
Defoliation Schedule Planner
Time your defoliation passes during veg and the transition to flower. Cannabis defoliation is high-impact — done right it dramatically improves canopy penetration and bud sites; done wrong it sets plants back a week. Calculator schedules passes against your training method and stage.
Veg connects to everything that follows
Cannabis vegetative questions
How long should I veg cannabis before flipping to flower?
For photoperiod genetics: 4–6 weeks is the home-grow sweet spot. Cannabis plants stretch 1.5–3× during the first 2–3 weeks of flower (the "stretch" phase). If you veg until the plants are at half your tent height, they'll fill the tent during stretch. Vegging longer pushes them into the light; vegging less leaves canopy capacity unused. Autoflowers ignore photoperiod — they veg for whatever 2–4 weeks their genetics dictate, then flower automatically. The Veg Duration Estimator (in development) will calculate this against your specific tent and genetics.
When should I top my cannabis plant?
For photoperiods: between the 4th and 6th node, when the plant has 4–6 sets of true leaves. Topping earlier stresses the plant before it has root mass to recover; later wastes the upper growth you'd be removing. Plan to top once for 2 main colas, twice for 4, three times for 8 — but every top adds 5–10 days of recovery before flower. Don't top autoflowers — they don't have time to recover before auto-flowering kicks in. LST (low-stress training) is the better technique for autos; the Training Timeline Planner (in development) will sequence topping vs LST schedules for you.
What pot size do I need for cannabis at each stage?
Rough guide: 16-oz solo cups for clones and seedlings, transplant to 1-gal at week 2, transplant to 3-gal at the start of veg, transplant to final 5–7 gal pot 1–2 weeks before flip. Final pot size correlates roughly with final plant height — about 2 gallons per foot of expected plant height. Fabric pots run ~25% larger than rigid plastic for the same root space because of air pruning. The Pot Size Calculator (in development) will sequence transplants based on your tent height target.
How many cannabis plants can I fit in my tent?
Depends entirely on training method. SOG (Sea of Green) packs plants tight — 4 per sq ft for autos, 4 per sq ft for small photos. LST: 1 photo per sq ft, 2 autos. ScrOG: 0.5 photos per sq ft, 1 auto — each ScrOG plant fills 2 sq ft of canopy. Untrained: 0.5 photos per sq ft. For a 4×4 (16 sq ft): 64 SOG autos OR 8 LST photos OR 4 ScrOG photos OR 8 untrained photos. The Plant Spacing Calculator runs this math against your tent and training plan. The current Grow Tent Sizer also handles plant-to-tent matching from the opposite direction.
Should I use ScrOG, LST, or just topping?
Depends on goals and experience. LST (low-stress training) is the best starter technique — tie down branches to encourage horizontal growth, no plant damage, recoverable from mistakes, works for autos and photos. Topping is more aggressive — cut the main stem to create multiple colas, requires recovery time, only do it on photoperiods with 5+ weeks of veg ahead. ScrOG is the highest-yield technique but needs commitment — install a screen at the canopy level, weave growth through it, requires consistent attention for 4+ weeks. First grows: LST. Second grow: add topping. Third grow: try ScrOG if you have the time.
How much should I water cannabis in veg?
Water by weight, not by schedule. Lift the pot — if it feels light, water until 10–20% runoff. If it still feels heavy, wait. Common starting point: water every 2–3 days for plants in 3-gallon pots during veg, scaling to daily by late veg as the canopy gets large. Soil and coco need different approaches — coco wants more frequent, smaller waterings (daily); soil prefers larger, less frequent (every 2–3 days). The Weekly Task Planner (in development) will include a watering log to help you track frequency. Until then: pick up your pots before and after watering to learn what wet vs dry feels like.