How Many Hours of Sunlight Do Plants Need?
Instant calculator + reference chart for plant sunlight hours by type. Full sun, partial shade, and shade requirements for 18 common plants — with grow-light equivalents.
- Data verified · June 2026
- Edited by Martín Rodríguez
- Formula verified by automated tests
- Private — runs on your device
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How to use this calculator
Follow this tool’s steps, then review its formula, assumptions, and limits below.
When to use this calculator
- Determining the best garden bed location for tomatoes, peppers, or squash that need 6–8 hours of direct summer sun to set fruit properly.
- Choosing the right windowsill (south-facing vs. north-facing) for indoor plants like pothos, snake plants, or orchids based on their light tolerance.
- Diagnosing why a houseplant is growing leggy, losing color, or dropping leaves — symptoms directly tied to receiving too few or too many sunlight hours.
- Planning a vegetable garden layout by mapping which yard zones receive full sun, partial shade, or full shade throughout the day using daily hour counts.
- Selecting companion plants for a mixed garden bed where taller crops like corn cast shade, reducing available hours for shorter neighbors like lettuce.
- Adjusting grow-light schedules (in hours per day) for indoor seedlings or hydroponic setups to replicate natural sunlight requirements.
Sunlight Hours by Plant: 18 Common Vegetables, Herbs & Houseplants
| Plant | Light Category | Min Hours/Day | Ideal Hours/Day | Notes |
|---|---|---|---|---|
| Tomato | Full Sun | 6 | 7–8 | Under 6 h cuts fruit set significantly |
| Pepper | Full Sun | 6 | 8 | Needs heat + light for ripening |
| Zucchini / Squash | Full Sun | 6 | 7–8 | Powdery mildew risk in shade |
| Basil | Full Sun | 6 | 6–8 | Bolts faster with excess heat |
| Lavender | Full Sun | 6 | 8+ | Mediterranean native, drought-tolerant |
| Strawberry | Full Sun | 6 | 8–10 | Fruit drops below 6 h |
| Blueberry | Full Sun | 6 | 8 | Requires acidic soil + full sun |
| Rose | Full Sun | 5 | 6–8 | Disease risk increases below 5 h |
| Succulents / Cacti | Full Sun | 6 | 8–12 | South-facing window or outdoors |
| Lettuce | Partial Shade | 3 | 4–6 | Bolts in full summer sun |
| Spinach | Partial Shade | 3 | 4–5 | Prefers cooler, filtered light |
| Mint | Partial Shade | 4 | 4–6 | One of few herbs tolerant of shade |
| Fern (outdoor) | Shade | 0–1 | 1–2 indirect | Burns in direct sun |
| Hostas | Shade | 0–1 | 1–3 indirect | Variegated types tolerate more |
| Pothos (indoor) | Shade | 2–4 indirect | 4–6 indirect | Tolerates fluorescent light |
| Snake Plant | Shade | 2 indirect | 4–6 indirect | Survives in low light |
| Orchid (Phalaenopsis) | Shade | 4–6 indirect | 6 indirect | No direct sun — burns leaves |
| Peace Lily | Shade | 2–4 indirect | 4–5 indirect | Lowest-light tolerant |
Fuente: USDA cooperative extension guidelines & University of Minnesota Extension – Selecting Plants for Shade. Hours refer to direct sunlight unless marked 'indirect'. Full Sun = 6+ h direct; Partial Shade = 3–5 h direct; Shade = under 2 h direct (mostly indirect/morning light).
Target Daily Light Integral (DLI) by Plant Category
| Light Category | Direct Sun Hours/Day | Target DLI (mol/m²/day) | Grow Light Hours Needed (low LED)* |
|---|---|---|---|
| Full Sun | ≥ 6 h | 20–30 | 16–18 h |
| Partial Shade | 3–6 h | 8–12 | 10–14 h |
| Shade | < 2 h (indirect) | 3–6 | 6–10 h |
Fuente: Purdue University Extension & Wikipedia – Daily Light Integral. *Grow light estimate based on a residential full-spectrum LED at 100–400 µmol/m²/s PPFD, using DLI = PPFD × hours × 0.0036. Direct midday sun ≈ 1,500–2,000 µmol/m²/s.
How it works
Sunlight Hours by Plant Type — Quick Reference
The three standard horticultural light categories, used on nursery labels and by the USDA:
| Light Category | Direct Sun Hours/Day | Typical Plants |
|---|---|---|
| Full Sun | 6–8 h (minimum 6) | Tomato, pepper, squash, basil, lavender, rose, succulents, strawberry |
| Partial Shade | 3–5 h | Lettuce, spinach, chard, mint, impatiens, camellia |
| Shade | 1–3 h (indirect/morning) | Fern, hosta, begonia, peace lily, pothos, snake plant |
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Plant-by-Plant Reference Table
Based on USDA cooperative extension guidelines:
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How It's Calculated
Plant sunlight requirements are expressed in daily hours of photosynthetically active radiation (PAR) received at the plant's canopy. The classification follows horticultural standards:
Season Adjustment: When the sun is lower in the sky (fall/winter), effective PAR hours drop even if clock-hours of daylight remain similar. A rough factor for 35–45°N latitude:
So a bed that gets 8 clock-hours of sun in July may deliver only ~4 effective hours in December — pushing a full-sun perennial into partial-shade conditions.
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Grow Light Equivalents
A typical residential full-spectrum LED grow light delivers 50–200 µmol/m²/s PPFD, while direct midday sun provides ~1,500–2,000 µmol/m²/s. To hit the same Daily Light Integral (DLI) as 6 outdoor sun hours, a low-intensity grow light may need to run 16–18 hours per day.
Formula: DLI (mol/m²/day) = PPFD (µmol/m²/s) × hours × 0.0036
Target DLI values: shade plants ~3–6 mol/m²/day; partial shade ~8–12; full sun crops ~15–25.
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Common Errors
1. Counting total daylight, not direct sun hours — A garden bed may have 12 hours of daylight but only 5 hours of unobstructed direct sunlight due to fences, trees, and buildings.
2. Ignoring seasonal sun angle changes — A "full sun" spot in June (sun angle ~70° at 40°N) can drop to partial shade in September (sun angle ~45°).
3. Treating "bright indirect light" as "partial sun" — Outdoors, partial sun = 3–6 hours of direct solar radiation (~10,000–25,000 lux). Indoors, "bright indirect light" may deliver only 500–1,000 lux. Not interchangeable.
4. Placing shade plants near heat-reflecting walls — A shaded spot may still radiate significant heat and reflect ambient light, stressing shade plants even without direct sunlight.
5. Neglecting canopy competition over time — Newly planted full-sun vegetables may get adequate light in spring, but neighboring tomatoes or corn casting shadows by mid-summer reduce hours for shorter companions.
Worked Example — Tomato Plant
Frequently asked questions
How many hours of sunlight does a tomato plant need per day?
What is the difference between full sun, partial shade, and full shade?
How many hours of sunlight do indoor plants need?
Can I use a grow light to replace natural sunlight hours?
Does the direction my window faces affect how many sunlight hours my indoor plant receives?
Why is my plant getting enough hours of light but still growing leggy (etiolated)?
Do sunlight requirements change with the seasons?
What happens if a shade-loving plant gets too many hours of direct sun?
How do I measure how many sunlight hours a specific spot in my yard actually receives?
Sources & references
Methodology & trust
jardineria calculator with its formula verified automatically against USDA National Agricultural Library – Grow It Guide, per our editorial policy and methodology.
Updated: June 2026. Parameters are verified periodically against the cited sources.
Calculations run 100% in your browser. We do not store or transmit your data.
Indicative results. For critical decisions, consult a professional.
Rodríguez, M. (2026). How Many Hours of Sunlight Do Plants Need?. Hacé Cuentas. https://hacecuentas.com/en/plant-sunlight-hours
Content licensed under CC-BY 4.0 — reuse it citing the source with a link to Hacé Cuentas.