What is bright indirect light, and does your window have it?
Bright indirect light means a spot with a lot of open sky in view, where the sun itself never falls directly on the leaves. It is the condition almost every plant label is written for, and it is far less common in apartments than the phrase suggests. A window facing the right way is not enough on its own: what is outside it and how far back the plant sits will move a spot two bands in either direction.
Answer five questions below and you get an estimate from 1 to 5, plus the part plant lists leave out: what will actually put out new growth there, what will merely hold on, and what will slowly go backwards no matter how carefully you water it.
Estimated light
roughly 11 to 25 foot-candles on a clear day
Under the 75 foot-candle floor. This is a spot for a lamp, not for a plant label that says low light.
The biggest limit here is which way the window faces.
- Will grow
- Nothing, reliably, without added light.
- Will survive
- A tough plant hangs on for months while quietly losing leaves. That is decline on a delay, not tolerance.
- Will decline
- Effectively everything, eventually.
An estimate from what you can see, not a meter reading. The foot-candle scale and the direction-and-distance figures behind it come from University of Illinois Extension. Saved on this device only.
The shadow test, if you want an answer in ten seconds
Hold your hand about a foot above the spot where the plant would sit, somewhere near the middle of the day, and look at the shadow:
- Hard edges, clearly defined. Direct sun. Good for succulents and cacti, too much for a fern.
- Soft but definitely there. This is bright indirect light, the condition most houseplants are sold for.
- Faint, or no shadow at all. Low light, regardless of how bright the room feels to you.
The test is crude and it depends on the weather that day, which is why the estimator above asks about the things that do not change: which way the window faces, what is blocking it, and how far away the plant is.
Why bright indirect light is rarer in apartments than it sounds
Orientation sets the ceiling. A south-facing window can deliver direct sun and a north-facing one essentially cannot. But three other factors decide how much of that ceiling reaches the plant, and two of them usually matter more than the compass.
Distance from the glass is the one people underestimate most. Step back from a window and two things happen at once: the light has further to travel, and the patch of sky the plant can see gets smaller. A shelf on the far wall of a bright room can receive a fraction of what the sill in front of it does. Your eyes compensate so well that the room still reads as bright, which is how plants end up in spots that look fine and are not.
What is outside comes next. A building across the street does not so much dim the light as remove most of the sky, and sky is where indirect light comes from. This is the most common reason an apartment window underperforms what its direction promises, and it is the reason this site exists.
What is on the glass is smaller but real. A sheer curtain is frequently the difference between a plant growing and a plant standing still.
Where these foot-candle numbers come from
Light for plants is measured in foot-candles, and the scale this tool uses comes from University of Illinois Extension, which is unusual in publishing both the levels and the window positions that produce them: low light at 75 foot-candles, medium at 150, high or bright at 300, and direct at 1,500.
The same page lists where those levels occur. Medium light is a north window directly in front of you, or an east or west window a few feet back, or a south window at three to ten feet. Low light is a north window a few feet away, an east or west window at three to ten feet, or a south window at fifteen to twenty. Those pairings are what the estimator is built on: the base values are read off that table, and the falloff with distance is derived from the south-window series. Checked against all nine of their combinations, it returns the band they assign in every one.
The published scales do not agree with each other, which is worth knowing before you treat any foot-candle figure as a threshold. University of Minnesota Extension puts low light at 50 to 250 foot-candles and medium at 250 to 1,000, which overlaps Illinois' medium and high bands almost entirely. Both are reputable. They are describing a gradient that does not have natural edges, and any site quoting one exact number as the definition of low light is quoting one committee, not a law of nature.
One consequence worth knowing before you change anything: a spot in a low band dries out slowly. The same watering habit that suits a bright windowsill will keep a dim corner permanently damp, which is how a light problem turns into a root problem. If a plant in a low band is already struggling, start with overwatering versus underwatering before buying a lamp, because the two look almost identical and the usual instinct makes the wrong one worse.
What the tool is guessing at
Being specific about this is the difference between an estimate and a number pulled out of the air.
- Sourced: the foot-candle levels, the base value for north, east, west, and south windows, and how fast light falls off with distance. All from the Illinois table above.
- Interpolated: northeast, northwest, southeast, and southwest. Illinois lists only the four cardinal directions, so those four sit between the neighbors on either side.
- Not sourced: how much a building opposite, a tree, a sheer curtain, or a dark wall takes away. These are reasoned from the fact that indirect light is sky light, and no published figures were found for them. They move the result, and they are the softest part of it.
- Weakest of all, the glass. Manufacturer material puts single clear glazing near 90 percent visible transmittance, double clear near 81, and low-e in the mid to high 70s, but no authoritative source could be found that covers windows generally. The reassuring part is that low-e coatings are described by the Efficient Windows Collaborative as “spectrally selective low-E glass due to their ability to reduce solar heat gain while retaining high visible transmittance”. They are built to block heat, not the light plants use, so they cost you less than the internet suggests.
A band is still an estimate, not a measurement
Everything above is derived from what you told it, and what you told it is a description rather than a reading. That is why the result is a range rather than a single figure: a precise number produced from six multiple-choice answers would be false precision, which is worse than a rough answer honestly labeled.
If you want a real number, a light meter or a phone meter app will give you one, and measuring at the exact spot and time of day beats any estimate. This tool is for deciding whether the corner you had in mind can support bright indirect light before you spend money on a plant that needs it.
Common questions about bright indirect light
What is bright indirect light?
Bright indirect light is a spot with a large amount of open sky in view, where the sun itself never lands directly on the leaves. In practice it usually means within a step or two of an unobstructed east, west, or large north window, or set back slightly from a south one. It is the default condition most houseplant labels are written for, which is why so many plants disappoint in rooms that do not have it.
How can I tell if I have bright indirect light without a meter?
Hold your hand about a foot above where the plant would sit, around midday. A hard-edged shadow with sharp outlines means direct sun. A soft shadow that is clearly there but blurred at the edges is bright indirect. A shadow you can barely make out means low light, whatever the room looks like to you.
Is a north-facing window bright indirect light?
It can be, if the window is large, the sky outside is open, and the plant sits close to the glass. Add a building opposite or move the plant a few steps back and the same window drops to low light. North windows are the most variable of the four directions, which is exactly why a single label like low light or bright indirect is not much use on its own.
Does a sheer curtain still count as bright indirect light?
A sheer curtain over a sunny window is the classic way to create bright indirect light, and it works. Over a window that was already indirect, the same curtain pushes it down to moderate. The curtain does not create light, it only softens what is arriving.
How far from the window is too far?
Light drops off much faster indoors than it looks like it should, because stepping back also shrinks how much sky the plant can see. A spot three or four steps into a room can receive a small fraction of what the sill receives, even though the room still reads as bright to you. Your eyes adjust; the plant does not.
Is this the same as measuring with a light meter?
No. This is an estimate built from things you can observe without buying anything, and it returns a band rather than a number. A light meter or a meter app gives an actual reading and is more accurate. If you want precision, measure. If you want to know whether the corner you had in mind is realistic, this is enough.