PLANTS · LIGHT
Plant Light Checker
Check whether the spot you have in mind is bright enough for a plant, see which of 50 common houseplants suit it, and find out which way to move a plant you already have.
Check a spot
Example
In the Northern Hemisphere, a spot 1 m from a regular east window with no curtain scores 60 × 0.75 = 45: bright indirect light, which suits a monstera or rubber plant. A snake plant would be on the bright side there. Add a sheer curtain and the score drops to 27, low indirect light. In the Southern Hemisphere, the same result comes from a west or east window, and a north window scores like a south window does up north.
How the estimate works
Nebraska Extension notes that if a south window in the Northern Hemisphere gets 100% light, east and west windows get about 60% and north windows about 20%. The tool starts from those scores (southeast and southwest 80, northeast and northwest 30 are site defaults) and lowers them with distance. Mississippi State University Extension explains that light can drop from 1,000 to 100 foot-candles within a few feet and that plants struggle more than 8 to 10 feet from a window, so the score stays the same up to 0.5 m, then ×0.75 at 1 m, ×0.5 at 1.5 m, ×0.3 at 2 m and ×0.15 at 3 m. Beyond 3 m the spot counts as too dark.
Larger windows let in more light (×1.2, small windows ×0.7). Curtains, blinds, a balcony above, nearby buildings and trees reduce it. A score of 70 or more is bright light, 35 or more bright indirect light, and 5 or more low indirect light. These cut-offs are site defaults chosen to match University of Minnesota Extension’s examples (north window = low, east window = medium, south window = high). Four or more hours of direct sun within 1 m raises bright indirect light by one step; almost no direct sun lowers bright light by one.
Signs of too little or too much light
With too little light, stems grow long and thin and lean toward the window, lower leaves drop and variegated leaves turn plain green. Too much light bleaches or scorches leaves. Move the plant one step at a time and watch it for a week or two.
This is an estimate from the window and distance, not a light meter reading. Season, time of day, floor and nearby buildings all change the real light, so check again when the season changes.
Frequently asked questions
What counts as bright indirect light?
A bright spot that direct sun does not reach, such as near an east window, a little back from a west window, or a few feet from a window facing the equator. This tool estimates it from the window and distance; it does not measure lux.
Why does the hemisphere matter?
In the Southern Hemisphere the sun is in the north, so north-facing windows are the brightest and south-facing ones the dimmest. Choosing Southern swaps north and south in the calculation.
How much does a curtain block?
Sheer curtains already cut a noticeable amount of light, and heavy curtains or blinds left closed during the day make even a window spot dim. The tool uses ×0.6 for sheer and ×0.2 for heavy curtains (site defaults).
Can my phone camera measure the light?
Not reliably. Phone cameras adjust exposure automatically, so they cannot give true brightness. Use a light meter at midday if you need a number.
More tools
Sources and last updated
- Nebraska Extension in Lancaster County, Let There Be Light… for Your Houseplants (checked October 27, 2026)
- University of Minnesota Extension, Lighting for indoor plants and starting seeds
- Mississippi State University Extension, Care and Selection of Indoor Plants
- Plant light needs come from the Houseplant Care Guide data; pet toxicity from the ASPCA lists. Diagonal direction scores, distance and curtain factors, cut-offs and the Southern Hemisphere swap are site defaults.
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