# How tall do cannabis plants get indoors?

> Indoor cannabis usually finishes about 60–150 cm (2–5 ft) tall, because the grower sets the height: a photoperiod plant grows 50–100% taller after the flip, stretchy cultivars up to 3×, so a plant flipped at 40–60 cm ends near 60–150 cm. Autoflowers usually fit a 140–160 cm tent. Outdoors, unrestricted plants reach about 1–5 m (3–16 ft).

- Canonical: https://genetixbay.com/knowledge/answers/how-tall-do-plants-get-indoors.html
- Topic: Basics · Type: Numbers
- Evidence: Grower practice · Status: Draft: awaiting expert review
- Full article: [The cannabis life cycle, stage by stage](https://genetixbay.com/knowledge/basics/life-cycle.md)
- Also asked as: How big do weed plants get? | Plant height indoors | Final height of a cannabis plant | How tall will my plant be after the flip?
- 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

Indoor cannabis usually finishes about 60–150 cm (2–5 ft) tall, because you decide. A [photoperiod plant](https://genetixbay.com/knowledge/glossary/photoperiod.md) grows 50–100% taller after the flip, and stretchy cultivars up to 3×, so final height ≈ height at the flip × 1.5–3. [Autoflowers](https://genetixbay.com/knowledge/glossary/autoflower.md) usually fit a 140–160 cm (4.6–5.3 ft) tent. *Grower practice*, anchored to [stretch](https://genetixbay.com/knowledge/glossary/stretch.md) research.

## Why

Veg height is your choice. A photoperiod plant stays vegetative under long days until you flip it, so [veg time](https://genetixbay.com/knowledge/glossary/veg-time.md) sets the starting height.

The stretch adds the rest. Under short days, stems and [internodes](https://genetixbay.com/knowledge/glossary/internode.md) lengthened fastest from about day 5 to day 10 [1]. A plant-patent description puts the gain at 50–100% over the first two to three weeks after induction [2]; growers report 1.5× to 3×.

Light shapes the plant. Higher light in veg gave shorter internodes and more compact plants [3]. A dim or distant light makes plants stretch and gap.

Outdoors, there's no ceiling. Unrestricted plants commonly reach 1–5 m (3–16 ft), depending on [genotype](https://genetixbay.com/knowledge/glossary/genotype.md) and season [4].

## The numbers

| Height at flip | Final, 1.5× | Final, 2× | Final, 3× |
|---|---|---|---|
| 30 cm (1 ft) | 45 cm | 60 cm | 90 cm |
| 45 cm (1.5 ft) | 70 cm | 90 cm | 135 cm |
| 60 cm (2 ft) | 90 cm | 120 cm | 180 cm |

| Tent height | Usable plant height (about) |
|---|---|
| 140–160 cm | 55–90 cm |
| 180–200 cm | 95–130 cm |

Usable height = tent − pot (~30 cm) − 30–45 cm light gap − fixture and hangers (~10–15 cm).

## What to do

1. Work out your usable height before you plant.
2. Flip photoperiods at about half of it; a third for very stretchy cultivars.
3. Train flat with [LST](https://genetixbay.com/knowledge/glossary/lst.md) from early veg.
4. Keep light strong enough to hold internodes short.
5. Keep a little headroom for the light to be raised in week 3.

## Common mistakes

- Vegging by the calendar and running out of room in week 3.
- Assuming the breeder's "medium height" fits your tent.
- Raising a weak light higher, which makes stretch worse.

## Related

- Full article: [The cannabis life cycle](https://genetixbay.com/knowledge/basics/life-cycle.md)
- Answers: [when to flip](https://genetixbay.com/knowledge/answers/when-to-flip-to-flower.md) · [plant too tall for the tent](https://genetixbay.com/knowledge/answers/plant-too-tall-for-tent.md) · [what size tent](https://genetixbay.com/knowledge/answers/what-size-grow-tent.md)
- Article: [Stretchy, leggy cannabis](https://genetixbay.com/knowledge/diagnosis/stretching.md)
- Terms: [stretch](https://genetixbay.com/knowledge/glossary/stretch.md) · [internode](https://genetixbay.com/knowledge/glossary/internode.md)

## Follow-up questions

**How much do plants stretch after the flip?** Cannabis plants usually stretch 50–100% in the first two to three weeks after the flip to 12/12, and grower reports range from about 1.5× to 3× the height at the flip. Stems and internodes lengthen fastest from about day 5 to day 10 of short days. Plan for it by flipping at about half the height you can fit.

**How do I keep my plants short indoors?** Keep cannabis plants short indoors by flipping early, at about half your usable height, and training them flat. Low-stress training bends the main stem sideways; topping and a net (SCROG) spread the canopy. Strong light close to the canopy also keeps internodes short, while a weak or distant light makes plants stretch and grow gappy.

**How tall should my grow tent be?** A grow tent for photoperiods should be about 180–200 cm (6–6.6 ft) tall, because plants commonly double in height after the flip. Autoflowers and short, trained plants fit a 140–160 cm (4.6–5.3 ft) tent. Allow for the pot, a 30–45 cm (12–18 in) gap to the light and the fixture itself when working out the plant's usable height.

## Sources

1. Alter H, Sade Y, Sood A, et al. 2024. Inflorescence development in female cannabis plants is mediated by photoperiod and gibberellin. Horticulture Research 11(11):uhae245. https://doi.org/10.1093/hr/uhae245
2. US Plant Patent PP30,434 (cannabis plant 'LW-BB1'), botanical description of post-induction stretch. https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/PP30434
3. Moher M, Llewellyn D, Jones M, Zheng Y, 2021. High light intensities can be used to grow healthy and robust cannabis plants during the vegetative stage of indoor production. Preprints 2021040417 (not peer reviewed). https://doi.org/10.20944/preprints202104.0417.v1
4. Small E. 2015. Evolution and classification of Cannabis sativa (marijuana, hemp) in relation to human utilization. Botanical Review 81:189-294. https://doi.org/10.1007/s12229-015-9157-3