How many lux does the middle of a room get?

In this measured room: 570 lux at midday on a clear day — under 3% of the window reading. Your room will differ in digits, rarely in pattern.

Is a phone accurate enough to measure plant light?

Not for absolute precision — but for sorting spots into tiers and comparing them, yes, and that’s the decision that saves plants.

What counts as bright indirect light?

In practice: at or near a decent window, out of the direct beam. The interior of a room almost never clears that bar, whatever your eyes say.

We Measured 6 Spots in One Room: Window vs. Corner

I’ve killed enough plants in spots that “looked fine” to finally stop trusting my eyes. So on a clear day around midday, I measured every spot in one living room where a plant could plausibly live — same hour, sensor facing up, roughly plant height, using a phone as a rough light meter.

The numbers

Spot	Reading
At the bright window	20,000 lux
1 m from the window	15,000 lux
2–3 m away, in window shade	3,500 lux
Middle of the room	570 lux
Darker side of the room	119 lux
The dark corner	18 lux

Bar chart of light in one living room across six spots at midday: 20,000 lux at the window falling to 18 lux in the dark corner — One living room, six spots, midday. Android phone ambient light sensor · clear day · sensor up, plant height.

That’s not a typo. The corner gets less than 0.1% of what the window gets. A thousand times less light, in the same room.

The part that should bother you

Standing in that corner, it doesn’t look dark. It looks like “a spot that could use a plant.” Human eyes adapt so smoothly that a 99.9% drop in light reads as “a bit dimmer” — meanwhile anything placed there is quietly starving.

The other number that got me: the middle of the room — where “bright indirect light” supposedly lives — sat at 570 lux, under 3% of the window. Most care charts put bright indirect at several thousand lux minimum. The middle of this room is not bright indirect. It’s a cave with good PR.

How rough are these numbers?

Rough, and that’s fine. I double-checked with a second phone: the absolute numbers differed — phone sensors are imprecise — but the pattern was identical. Every step away from the glass costs you most of what’s left.

None of this is lab-grade, and it doesn’t need to be. For deciding where a plant can live, the tier a spot falls into matters far more than the third digit of a lux reading. Rough numbers taught me more than years of confident guessing.

What this means for your plants

The room is not the light environment. The spot is. “My living room is bright” is a sentence about the window, not the shelf.
Distance is the biggest lever you control. Moving a plant one meter toward the glass can multiply its light several times over — a bigger intervention than any fertilizer.
If a plant keeps declining and the watering checks out, measure the light before changing anything else. That rule alone would have saved most of the plants I’ve lost.
Your eyes are the least reliable instrument in the room. Not a character flaw — just biology. Use a sensor.

Measure your own room (it takes two minutes)

Measure, don’t guess.Pick a clear day, same hour for every spot. Set your phone down at each place a plant could live — sill, shelf, table, corner — at pot height. Compare the pattern, not the digits. That habit is the entire reason GrowSpot exists — and the free spot checker on this site is the ten-second version.

I Measured the Light in 6 Spots of One Living Room. The Window Gets 1,000× More Than the Corner.

The numbers

The part that should bother you

How rough are these numbers?

What this means for your plants

Measure your own room (it takes two minutes)

Questions, answered honestly

Find the right spot.