Plant Spacing & Layout

Sun Hours Calculator

Enter how many hours of direct sun your spot gets and what you want to grow, and this calculator tells you whether the light is excellent, workable, or too low — plus which crops will thrive there.

Count the hours your garden gets direct sun on a clear summer day

How to use the sun hours calculator

Light is the one growing condition you cannot buy in a bag. Before you invest in plants, it pays to know whether your chosen spot can actually support them. Enter the number of hours of direct sun the area gets on a clear summer day, choose what you want to grow, and pick the season. The calculator compares your light against each crop's needs and returns a clear verdict — excellent, workable, or too little — along with a short list of crops that will thrive in exactly that amount of light.

What "direct sun" really means

The hours that matter are hours of direct, unobstructed sunlight falling on the plant, not general daylight. A bright spot in the open shade of a wall may feel sunny to you but deliver very little of the intense light a tomato needs. As a rule of thumb, full-sun crops want 6 to 8 hours, moderate crops manage on 4 to 6, and shade-tolerant greens and herbs get by on 2 to 4. Count only the time the spot is genuinely in the sun, and be honest about shadows cast by fences, buildings, and trees.

Why the season changes the answer

The same patch of ground is not equally bright all year. In spring and fall the sun rises lower in the sky, days are shorter, and nearby trees may still be bare or already turning — so the usable light is noticeably weaker than at the summer solstice. This tool applies a seasonal adjustment so that a spot which is perfect for tomatoes in July is correctly flagged as marginal for the same crop in cooler shoulder seasons. If you garden mainly in spring and fall, lean toward leafy greens and other crops that accept lower light.

Making the most of the light you have

If your verdict is borderline, small changes add up. Thinning or limbing up nearby shrubs and tree branches can open the canopy and add an hour or two of direct sun. Light-colored gravel, pale fences, or reflective mulch bounce extra light onto plants, and growing in containers lets you chase the sun by moving pots as the season shifts. Pairing the right crop with the right spot — sun lovers in the brightest beds, greens and shade plants in the dimmer corners — is the simplest way to get a productive garden from the light you already have.

Frequently Asked Questions

Full sun means at least 6 hours of direct, unobstructed sunlight per day, and many fruiting crops do best with 8 or more. "Part sun" or "part shade" generally means 3 to 6 hours, while "full shade" is under 3 hours of direct sun (often with bright, indirect light the rest of the day). The numbers on plant labels almost always refer to direct sun, not ambient daylight.
Pick a clear day and check the spot every hour from morning to evening, noting when it is in direct sun versus shade, then add up the sunny hours. Apps and stick-in sensors can automate this. Measure during the season you plan to grow, because the sun sits lower and trees may leaf out or drop leaves, changing the picture dramatically between spring and midsummer.
Yes — just match the crop to the light. Leafy greens such as lettuce, spinach, and kale, along with many herbs like mint, parsley, and cilantro, crop reasonably well on 3 to 4 hours. Root vegetables need a bit more, around 4 to 6 hours. Fruiting crops like tomatoes, peppers, and squash genuinely need 6 to 8 hours, and no amount of care fully substitutes for that light.
Days are shorter and the sun sits lower in spring and fall, so the same garden spot delivers less usable light energy than it does at the summer peak. The tool applies a 0.8 multiplier to approximate that drop, giving a more realistic suitability check for shoulder-season planting. In summer it uses your hours as entered.
A spot with 3 to 4 hours of direct sun is best for shade-tolerant leafy greens (lettuce, spinach, kale, chard), shade-friendly herbs (mint, parsley, cilantro), and shade ornamentals like hostas and impatiens. You can stretch root crops here too, though they will size up more slowly. Avoid tomatoes, peppers, melons, and other heat-loving fruiting plants.
It can. Morning sun dries dew quickly and reduces disease, and is gentler in hot climates, making it ideal for greens and many flowers. Afternoon sun is more intense and better for heat lovers like tomatoes and peppers, but it can scorch tender plants in very hot regions. When totals are borderline, the quality and timing of those hours tips the balance.

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GardenCalc Editorial Team

Horticulture Writers & Master Gardeners

Our calculators and guides are written and fact-checked by gardeners with hands-on experience in vegetable production, soil management, and home landscaping.