Houseplant Light Analyzer
Updated · Sproutly
A bright-looking room can still have a dim plant shelf. Describe the exact spot where the leaves sit to get a starting recommendation. This tool explains placement; it cannot measure lux from a room description.
What the result means
The tool uses simple placement rules. No window daylight leads to a grow-light recommendation. Observed sunbeams take priority over compass direction. If you have not checked for sun, it asks you to observe; otherwise, distance and an obstructed sky view flag potentially limited daylight.
For positions close to a window, hemisphere helps interpret direction. A south-facing window often receives more sun in the Northern Hemisphere; a north-facing one plays that role in the Southern Hemisphere. Near the equator, seasonal sun position makes a simple north/south rule unreliable.
| Description | What to look for | What it does not tell you |
|---|---|---|
| Direct sun | Sunbeams fall on the leaf; its shadow has a distinct edge. | A brief sunbeam does not mean all-day high light. |
| Indirect light | The plant sees illuminated sky or reflected light without sunbeams on its leaves. | Indirect light can be dim or bright. |
| Low light | Relatively little useful light reaches the plant during the day. | Low-light tolerant plants still need enough light to sustain growth. |
Measure at leaf height
- Use a light meter, or a phone app as a rough comparison tool. Follow the device instructions for sensor orientation; do not shade the sensor with your hand.
- Measure where the leaves sit, not against the window. Note the time, weather and whether the reading was in a direct sunbeam.
- Repeat in the morning, around midday and later in the afternoon. Compare the current shelf with a position closer to the glass.
- Repeat after a seasonal change or when trees outside leaf out. A single sunny-noon reading can miss a mostly dim day.
Lux measures visible light at a moment in time. It does not measure the total light received over a day. Phone sensors differ, and readings under colored grow lights are especially hard to interpret. There is no single lux cutoff that turns indirect light into direct sun.
For plant groups and supplemental lighting, see University of Minnesota Extension’s indoor-lighting guide.
Make one change and watch new growth
If growth is leaning or the gaps between leaves are lengthening, try a closer position first. Photograph the plant and record the move. New growth is more useful feedback than an already damaged leaf, which will not repair itself.
Move gradually into stronger sun. A plant raised under nursery shade can scorch when placed directly in a hot window, even if the species tolerates sun once acclimated. Also check heat at the glass and how quickly the pot dries after the move.
A window is a broad opening, not a point lamp. Reflections, window size and sky visibility affect light loss across a room; doubling the distance does not reliably divide window daylight by four. For a grow light, use the manufacturer’s coverage and distance guidance, plus the plant’s response.
Frequently Asked Questions
Strong ambient light without sunbeams falling on the foliage. A position near a bright window can provide it, but the same distance from a shaded or small window may be too dim. Observe the light over the day and compare measurements at leaf height.
Yes. Window size and obstructions matter, and north-facing windows have a different sun exposure in the Southern Hemisphere. Do not reject a window based on direction alone.
Choose “No window daylight.” The tool will recommend supplemental lighting rather than suggesting that a shade-tolerant plant can grow in darkness. Ordinary room lamps are not automatically adequate grow lights.
Your answers describe a location, not a light measurement. Assigning a precise lux range would imply more certainty than the inputs support. Use a meter for a reading and repeat it across the day.
Sources & further reading
This guide combines the references above with practical decision steps for home growers. Conditions and cultivars vary. How we approach plant guidance · Suggest a correction