What is left at the end depends on a lot of things, and the light is only the strongest of them. That is why this calculator gives you a range instead of a wishful number. Free, no sign-up.
What counts is the actual power draw, not the number in the product name — a light sold as “600 W” often pulls only 100 to 150 watts. Work with the marketing figure and you will expect four times what is possible.
0.7–1.0 g/W · 5.9–8.5 oz
Freshly cut flower is three quarters water. What is left after drying is the number that counts.
The method here mainly stands for speed: what dries slowly keeps more weight. Dense flower loses less than airy flower — with sativa-leaning strains expect the lower end.
4.4 oz
| Light | Beginner | Intermediate | Experienced |
|---|---|---|---|
| Small tent (2 × 2 ft) 100 W | 40–70 g 1.4–2.5 oz |
70–100 g 2.5–3.5 oz |
100–130 g 3.5–4.6 oz |
| Medium tent (2.5 × 2.5 ft) 240 W | 96–168 g 3.4–5.9 oz |
168–240 g 5.9–8.5 oz |
240–312 g 8.5–11.0 oz |
| Large tent (3 × 3 ft) 480 W | 192–336 g 6.8–11.9 oz |
336–480 g 11.9–16.9 oz |
480–624 g 16.9–22.0 oz |
Every figure is a range, because a single number would always be wrong here. Strain, pot size, training and climate shift the result further — in both directions.
These calculators give you reference values for your own judgement. They replace neither a measurement on site nor expert advice — all figures without guarantee.
The most common measure in indoor growing is grams per watt: divide the dry weight by the power the light actually draws. 240 grams from a 240-watt fixture is 1.0 g/W.
It is a useful figure for comparing your own runs — and a poor promise about the next one. The values you find online run from 0.4 to over 2.0 g/W, and both ends are true: for different people, different strains, different rooms. Turn that into a single number and you have built a forecast on the widest spread in the whole hobby.
It gets worse when you compare the calculators themselves. One of the sites measured for this page states 0.41 g/W as its efficiency figure; another calls 1.0 g/W solid and puts modern LEDs at 1.5 to 2.0. That is a factor of five between two tools answering the same question — and each of them hands you one confident number.
This calculator gives you a range instead, and the range is deliberately set at the cautious end of the published figures. An expectation that gets exceeded costs nobody anything. One that does not get met costs you a season of wondering what you did wrong.
Before any of the above matters, most estimates go wrong at the very first input. A light advertised as “600 W” usually does not draw 600 watts — that number often refers to the combined rating of the LED chips, which are run well below their limit on purpose.
A typical “600 W” panel pulls somewhere between 100 and 150 watts from the wall. Feed the marketing figure into a yield calculator and it will promise you four to six times what the fixture can actually deliver. That single mistake explains a good share of the disappointed forum posts on the subject.
The real figure is in the data sheet under “power draw”, or on a plug-in power meter. It is the same number you need for the electricity cost calculator — worth measuring once and writing down.
The light sets the ceiling. Everything else decides how close you get to it.
The strain is the biggest single factor after the light, and it is set before you start. Breeder figures are honest often enough, but they are measured under good conditions — treat them as the upper end, not the expectation.
Pot size and root space cap the plant long before the light does. A plant in a 5-litre pot cannot use the light a 20-litre pot would let it use, no matter how good the fixture is.
Training — topping, LST, SCROG — is the lever with the best ratio of effort to result, because it spreads the canopy across the area the light actually covers. A single tall cola under a wide fixture wastes most of what the light puts out.
Climate decides whether the plant can use the light at all. If VPD is off, the stomata close and the photons go to waste — that is what the VPD calculator is for. Same for the daily light integral: more intensity only helps while the plant can process it, which the DLI calculator shows.
The number on the scale right after cutting is not your harvest. Fresh flower is 75 to 80 percent water, and all of it goes.
What remains is roughly a fifth to a quarter of the wet weight — a ratio of about 4:1 to 5:1. 1,000 grams wet becomes 200 to 250 grams dry. Anyone quoting a harvest in wet grams is quoting a number four times too high, usually without meaning to.
The drying method shifts that a little, and mostly through speed: hung whole on the branch, the flower dries slowest and keeps the most weight; in bags it goes fastest and keeps the least. Dense indica-leaning flower loses less than airy sativa. None of that changes the water content much — it changes how much of the remaining moisture stays bound in the flower.
And the direction of that trade-off matters: drying too fast costs quality, not just weight. The extra grams from a slow dry are the ones you actually want.
An estimate is what you use before you have data of your own. After three cycles in the same tent with the same fixture, your own numbers beat any calculator — including this one.
By then you know your g/W, and you know it for your room, your strains and your habits. From that point the useful question changes from “how much will I get?” to “what did I change, and what did it do?”
Which is the point of writing it down as you go: dry weight per cycle, next to the wattage, the strain and what you did differently. Three cycles of that is worth more than every yield calculator on the internet put together.
Between roughly 40 and 150 grams of dry flower per plant, depending on light, pot size, training and experience. The plant count matters far less than the area and the light — four plants under the same fixture do not yield four times what one does, they split what the light provides.
Dry weight divided by the power the light actually draws from the wall. 240 grams from a 240-watt fixture is 1.0 g/W. It is a good measure for comparing your own runs against each other, and a poor one for predicting the next — the published values run from 0.4 to over 2.0.
Not for a normal tent. Figures above roughly 1.5 g/W come from optimised rooms with CO₂ enrichment, high-efficiency fixtures and years of practice on strains chosen for output. As a planning figure they are misleading. Beginners land around 0.4 to 0.7 g/W, and there is nothing wrong with that.
Divide by four to five. Fresh flower is 75 to 80 percent water, so roughly a fifth to a quarter remains. 1,000 grams wet becomes 200 to 250 grams dry. The calculator above does it with the drying method factored in.
Because most of what you weighed was water. Losing 75 to 80 percent is normal and expected — it is not a sign that anything went wrong. The number that counts is the one after drying, which is also the only one worth comparing with anyone else.
No. What sets the ceiling is the area and the light above it, not the number of plants sharing it. More plants can help you fill the canopy faster, especially with SOG, but past a certain point they only compete for the same photons — and cost more in soil, nutrients and work.
Training is the best ratio of effort to result: topping and LST spread the canopy across the area the light actually covers, instead of one tall cola wasting the edges. After that, get the climate right — if VPD is off, the plant cannot use the light it already has. Both cost nothing but attention.
Yes. This calculator uses the same ranges and the same wet-to-dry factors as the yield calculator in the CRIS app. In the app you can also record the actual result of each cycle — and after three of them your own figures are better than any estimate.
CRIS records what each cycle actually produced, next to the wattage, the strain and what you changed — so the next estimate comes from your own tent instead of a table. Offline, no account.