Will my mattress fit up the stairs?

How to measure

1. Stair width: the narrowest point you'll carry through, usually from the handrail to the opposite wall.
2. Headroom: stand a tape on the front edge of a step and measure straight up to the ceiling. Do it where the ceiling is lowest, which is often a beam or the edge of the floor above, near the bottom of the stairs.
3. Ceiling over the landing: from the landing floor straight up to the lowest point above it.
4. The mattress: the label usually gives the size; a tape across the widest point is better. Thickness is the height of the mattress lying flat.

How the check works

1. Going up: a mattress goes up long end first, so only its width and thickness have to pass. On its side, the width has to fit under the ceiling. Because the stairs slope, the room square to the stairs is less than the headroom you measured: about 0.8 of it on stairs of ordinary steepness (about 37 degrees). The check also tries it flat and leaned over at every angle in between, and picks the one with the most room.
2. A turn at a landing: it can be stood on its end, which needs a ceiling over the landing taller than the mattress is long, or pivoted on its side around the corner. Both are worked out from the stair width, taking the landing to be as deep as the stairs are wide. A turn back is two of these turns.
3. Room to spare: with less than an inch left over, it's marked too tight to count on, because hands and walls take room too.
4. What it can't see: a light fixture, a newel post, a low beam halfway up, or stairs steeper than usual. If your stairs are steep, expect less room than shown. A mattress that bends can often go where this says no, and a box spring can't.

Sources: no outside facts. This is geometry from your measurements. The mattress sizes are common U.S. sizes, given as a starting point, and the stair steepness is a typical figure, not a rule.