# How much yield should I expect per watt or per square foot?

> Expect roughly 100–500 g of dry flower per square metre (about 10–50 g, or 0.3–1.6 oz, per square foot) indoors, rising with light; well-run research rooms at 750–900 µmol/m²/s measured 500–750 g/m². Worked back from those trials, that is roughly 0.7–2 g per watt of efficient LED. A 4 x 4 ft tent therefore gives about 150–700 g, set mainly by canopy light.

- Canonical: https://genetixbay.com/knowledge/answers/grams-per-watt.html
- Topic: Basics · Type: Numbers
- Evidence: Supported · Status: Draft: awaiting expert review
- Full article: [PPFD and DLI by stage, with the evidence](https://genetixbay.com/knowledge/environment/ppfd-dli-by-stage.md)
- Also asked as: Grams per watt | Yield per square foot | How much will a 4x4 yield? | What is a good g/W?
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Short answer

Indoors, expect roughly 100–500 g of dry flower per m² (about 10–50 g, 0.3–1.6 oz, per ft²), rising with canopy light. Well-run research rooms reached 500–750 [g/m²](https://genetixbay.com/knowledge/glossary/yield.md). Worked back from the trials, that's about 0.7–2 g per watt of efficient [LED](https://genetixbay.com/knowledge/glossary/led.md). *Supported* for the light response; the g/W range is our arithmetic.

## Why

Yield follows light. Dry flower rose linearly from 116 g/m² at 120 [µmol/m²/s](https://genetixbay.com/knowledge/glossary/ppfd.md) to 519 g/m² at 1,800 µmol/m²/s [1], and a second trial found the same proportional response [3]. Another group measured 500–750 g/m² at 750–900 µmol/m²/s and 0.22–0.36 g per mole of photons [2].

Watts become photons through [efficacy](https://genetixbay.com/knowledge/glossary/photon-efficacy.md). Good LEDs exceed 2.5–3 µmol/J [4]. At 2.5 µmol/J, an average 900 µmol/m²/s needs about 360 W per m² of fixture, if the light lands on the canopy.

So g/W is a ratio of two numbers you can estimate. At about 300 g/m² under 450 W/m² (a less efficient fixture), you get ~0.7 g/W. At 720 g/m² under 360 W/m², ~2 g/W. Tent walls and edges waste some light, so home tents sit lower.

## The numbers

| Canopy light (µmol/m²/s) | Dry yield, g/m² | g/ft² | 2 x 2 ft tent | 4 x 4 ft tent |
|---|---|---|---|---|
| ~120 (weak) | ~115 | ~11 | ~40 g | ~165 g |
| ~600 | ~230 | ~21 | ~80 g | ~330 g |
| ~900 | ~300 | ~28 | ~110 g | ~430 g |
| 750–900, dialled in [2] | 500–750 | 46–70 | 180–270 g | 720–1,080 g |
| ~1,800 (very high) | ~520 | ~48 | ~185 g | ~750 g |

Rows 1–3 and 5 interpolate the linear response in [1]; cultivars differ.

## What to do

1. Use g/m² to compare grows; quote g/W only with the fixture's wall watts.
2. Measure average PPFD across the canopy, not the centre point.
3. Raise light gradually towards 800–1,200 µmol/m²/s in flower.
4. Buy efficacy (µmol/J), not "equivalent watts".

## Common mistakes

- Using a fixture's marketed "equivalent" wattage.
- Comparing g/W across different run lengths.
- Chasing g/W with light the plants can't use without CO₂.
- Expecting more light to raise [THC](https://genetixbay.com/knowledge/glossary/thc.md): it raises grams, not potency [1].

## Related

- Full article: [PPFD and DLI by stage](https://genetixbay.com/knowledge/environment/ppfd-dli-by-stage.md)
- Answers: [yield per plant](https://genetixbay.com/knowledge/answers/how-much-does-one-plant-yield.md) · [what wattage for my tent](https://genetixbay.com/knowledge/answers/what-wattage-light-for-my-tent.md) · [increasing yield](https://genetixbay.com/knowledge/answers/how-to-increase-yield-indoors.md)
- Terms: [grams per watt](https://genetixbay.com/knowledge/glossary/grams-per-watt.md) · [photon efficacy](https://genetixbay.com/knowledge/glossary/photon-efficacy.md) · [yield](https://genetixbay.com/knowledge/glossary/yield.md)

## Follow-up questions

**Is grams per watt a good measure?** Grams per watt is a rough measure. It mixes the light fixture's efficiency with the grower's skill and the run length, so a long-flowering cultivar or an efficient LED inflates it. Grams per square metre is better for comparing grows, and grams per mole of photons is the most physical: one trial measured 0.22–0.36 g of dry flower per mole.

**How much will a 4x4 tent yield?** A 4 x 4 ft (1.44 m²) tent yields roughly 150–700 g of dry flower, depending mostly on canopy light. At about 300 g/m², a reasonable target for moderate light, that's around 430 g (15 oz). Research rooms at 750–900 µmol/m²/s reached 500–750 g/m², about 720–1,080 g in a 4 x 4, but a first grow should plan on the low end.

**Does more light always mean more yield?** More light meant more yield in the best indoor trial: dry flower rose in a straight line from 116 to 519 g/m² as canopy light rose from 120 to 1,800 µmol/m²/s at ambient CO2, with no change in potency. In practice, above about 1,200 µmol/m²/s without added CO2 plants often show stress, and each extra gram costs more electricity.

## Sources

1. Rodriguez-Morrison V, Llewellyn D, Zheng Y, 2021. Cannabis yield, potency, and leaf photosynthesis respond differently to increasing light levels in an indoor environment. Frontiers in Plant Science 12:646020. https://doi.org/10.3389/fpls.2021.646020
2. Westmoreland FM, Kusuma P, Bugbee B, 2021. Cannabis lighting: Decreasing blue photon fraction increases yield but efficacy is more important for cost effective production of cannabinoids. PLoS ONE 16(3): e0248988. https://doi.org/10.1371/journal.pone.0248988
3. Llewellyn D, Golem S, Foley E, Dinka S, Jones AMP, Zheng Y, 2022. Indoor grown cannabis yield increased proportionally with light intensity, but ultraviolet radiation did not affect yield or cannabinoid content. Frontiers in Plant Science 13:974018. https://doi.org/10.3389/fpls.2022.974018
4. Kusuma P, Pattison PM, Bugbee B, 2020. From physics to fixtures to food: current and potential LED efficacy. Horticulture Research 7:56. https://doi.org/10.1038/s41438-020-0283-7