Cannabis Yield Calculator
A grounded estimate of what your space can carry, and the genetics worth putting in it. Tents, glasshouses, a corner of the section — all of them.
Work It Out
The Numbers People Ask For
From a 120×120cm tent?
225–450g
a cut, under LED
How many per m²?
1–16
1–2 trained large, up to 16 grown small
Off one plant?
30–140g
indoors, depending on the cultivar
From a 60×60cm tent?
55–115g
a cut, under LED
From an autoflower?
30–115g
a plant, over 8–10 weeks
What a Grow Actually Produces
Four things set the number: how much floor you are working with, what is lighting it, what you planted, and how many times you have done this before. Under LED, a square metre run properly returns somewhere around 155 to 305 grams; the same metre under HPS can reach 230 to 380. A plant in the ground has the widest spread of all — 30 grams to well past 140, decided mostly by how long your season runs.
Those bands are the starting point, then the tool shifts them for how long you have been growing and what type of seed you are running. Autoflowers trade size for turnover — up to four cycles indoors in a year — while a photoperiod plant puts more weight on one harvest.
Yield by Light Source, Per Square Metre
| What is lighting it | Yield / m² | Best For |
|---|---|---|
| LED | 155–305 g/m² | Efficient, and runs cooler |
| HPS | 230–380 g/m² | Raw intensity, decades of use behind it |
| CFL | 75–155 g/m² | Cupboards and side lighting |
| Sunlight (Outdoor) | 230–610 g/m² | No ceiling but the season |
Assume a grow that is actually looked after; a neglected one lands under the bottom of these. Feeding, humidity and temperature, and how you shape the canopy are what move you up inside them.
Four Levers Worth Pulling
Start With the Right Plant
Nothing you do later compensates for genetics that were never bred to carry weight.
High-yield genetics →Flatten the Canopy
Tying branches out, topping, or running a screen puts light on many sites instead of one.
How to train →Give It Enough Light
Up to a ceiling, more light means more flower. LED and HPS both get there.
Choosing a light →Feed It Consistently
Steady, stage-appropriate feeding beats heavy feeding, and beats erratic feeding by a wide margin.
Feeding guide →Genetics Bred for Weight
No amount of light rescues a plant that was never bred to carry weight. Some lines were, and they show it when the conditions are decent. Whether you are after quick turnover with autoflowers or the heaviest single cut from a photoperiod plant, this is the decision made before anything else.
Under Lights or Under the Sun
💡 Indoor Growing
- • Usually 155–380 g from a square metre
- • Two to four cuts a year
- • The weather is whatever you set it to
- • July is the same as January
- • Costs more to set up, loses less to chance
☀️ Outdoor Growing
- • Usually 30–140 g a plant, sometimes far more
- • One harvest, in autumn
- • The light is free
- • Nothing caps the height but the fence
- • A wet March can take the lot
How Much to Trust the Number
It is an estimate, and it is deliberately an unexciting one. Floor area, light source, seed type and experience all feed into it. What it cannot see is your room: how you feed, how stable the temperature and humidity are, whether you train, and the particular quirks of the cultivar in front of you.
The bias is downward on purpose. A first grow generally lands near the floor of the range; someone on their sixth, running genetics bred for weight and training the canopy, will sit at the top or past it. The optimised figure is that second grower, not the average one.
The bands come from published horticultural figures for cannabis under each light type, not from a survey of our own customers. We have not run one, so we are not going to quote one. Where a breeder publishes a figure for a specific cultivar it sits on that product page, clearly attributed.
Use it to plan a space, not to set an expectation. The figure that matters is the one you record yourself, and it climbs each season as you learn the room. Weigh it against what the cultivar is capable of, what you are lighting it with, and whether you shape the plant at all.
Frequently Asked Questions
What comes out of a 120×120cm tent?
That is 1.44 square metres, and under LED someone with a few grows behind them will usually take 225 to 450 grams off it. A first attempt tends to land nearer 170 to 340. Genetics bred for weight, and a canopy that has been trained flat, are what move you up the range.
How many plants fit in a square metre?
Anywhere from one to sixteen, and the spread is not a hedge — it is the whole decision. Vegetate a plant for six weeks and train it wide and one will fill the metre on its own. Flip small plants almost straight away, sea-of-green style, and eleven to sixteen is normal. Most people with a 120×120cm tent settle somewhere between four and nine, set by pot size more than anything else.
LED or HPS?
HPS still shows a higher band on paper — 230 to 380 grams a square metre against 155 to 305 for LED — but the gap has narrowed to the point where the running cost decides it for most people. LED draws 30 to 40 per cent less power and throws far less heat, which matters in a small New Zealand room in February. Unless you have a reason to want the heat in winter, LED.
And a plant in the ground?
Thirty grams to well over 140, with season length doing most of the work. Northland, Auckland and the Bay of Plenty run long enough that a plant can get genuinely large before the light turns; the same seed in Southland is racing an April frost and finishes far smaller. Big Bud and Critical Mass are the usual answers where there is time to use them.
Do autoflowers really yield less?
Per plant, clearly: roughly 30 to 115 grams against 55 to 225 for a photoperiod plant. Per year, not necessarily. An eight to ten week cycle lets you run three or four rounds indoors in the time a photoperiod grow takes to produce one or two, and the annual totals often end up level or better.