Guide
Measuring angles, understanding angles
Furniture is built for 90 degrees. Your corner probably doesn't have them. Before you put the next shelf, countertop, or cabinet against a corner, one question is worth asking: how crooked is it, really? Here are three methods — from rough to precise. You won't need anything you don't already own.
Method 1: The folded sheet of paper
Every sheet of paper has perfect 90-degree corners — that's an industrial standard, and more reliable than any eye. Hold a paper corner into your wall corner at eye level. If a gap opens between paper and wall at the top or bottom, the angle deviates: a gap toward the room means more than 90 degrees, a gap toward the corner means less. It takes ten seconds and answers the most important question: is my corner even straight?
Method 2: The diagonal
For a real number, all you need is a folding rule and a pencil. From the corner, measure exactly 50 centimetres along each wall and mark both points. Then measure the straight line between the two marks — the diagonal. At exactly 90 degrees it is 70.7 centimetres. Less means your corner is tighter; more means it opens wider. As reference points: 67.6 cm is roughly 85 degrees, 70.7 cm is 90, 73.7 cm is about 95. You don't need millimetre precision — the tendency is enough.
Method 3: The phone
The spirit-level app on your smartphone measures inclines surprisingly well — angles between two walls, however, only indirectly. Hold the phone flat against one wall, note the value, then against the other. The difference from theory tells you the deviation. It remains an estimate: walls are rarely flat, and one reading in one spot doesn't speak for the whole corner. For a first impression, it's plenty.
What's normal?
More than you'd think. Even in new buildings, construction tolerances allow visible deviations — and in old buildings, where a house has settled over decades, a few degrees off is the rule rather than the exception. A corner at 87 or 93 degrees is not a construction defect and no cause for concern. It's the normal case nobody talks about — because the furniture industry pretends it doesn't exist.
Your wall is not the problem. Measure it once, know its number, and then buy — whatever it is you're buying.