Inside Measurements by Overlapping Tapes

Adding two tape readings that meet at a round number to read a wall-to-wall span exactly.

2 takes from different creators

Measure Wall to Wall Accurately by Marking 10 Inches and Adding It Back

A tape bent into the far corner reads short and you can't see the number anyway. Mark 10 inches out from one wall instead, hook the tape on the opposite wall and read to the mark, then add 10 to what you read.

measure between two walls, tape measure bends in the corner, inside dimension trick, cut trim to fit wall to wall, measurement comes up short

beginner Tools: tape measure, pencil Added Aug 23, 2026
Watch the instagram video by @turnershomeimprovements (opens in new tab)

The Problem

An inside measurement — wall to wall, jamb to jamb, inside a cabinet opening — is the one a tape measure is worst at. Hook the tape in one corner and the last few inches bend up the far wall, so the blade curves away from the surface you're trying to reach and the number you want is on the part that's bent. Most people push the tape into the corner, eyeball the bend, and round.

That guess goes straight into a piece of trim or a shelf. A quarter inch long and the piece won't drop in; a quarter inch short and you're looking at the gap for as long as you own the room.

The Technique

Take the corner out of the measurement entirely by putting your reference point somewhere flat.

  1. Hook your tape on one wall and mark the wall — or the floor — at exactly 10 inches.
  2. Move to the opposite wall. Hook the tape there and read across to your mark.
  3. Add 10 inches to what you read. That's the span.

If the second reading is 43-1/4, the wall-to-wall dimension is 53-1/4. Nothing was bent, nothing was estimated, and both numbers were read off a flat run of tape with the blade lying against the surface.

Ten is arbitrary — it's just an easy number to add in your head under a cabinet. Any round number works as long as you use the same one at both ends of the arithmetic.

Pro tip: Mark the 10 inches on the floor rather than the wall when you're measuring for baseboard or a cabinet run — the wall may be getting painted, and a pencil line on the floor disappears under the trim you're about to install.
Watch the instagram video by @turnershomeimprovements (opens in new tab)

Measure an Inside Span by Adding Two Overlapping Tape Readings

When a tape can't read an inside span in one shot — the hook is in one corner and the case blocks the other — measure from one side to a round number like 30, then pull from the other side to the same spot and add the two readings: 30 plus 25-3/4 is a 55-3/4 span.

measure between two walls exactly, tape bends in corner, inside measurement trick, wall to wall trim length, add tape case width

beginner Tools: tape measure Added Aug 6, 2026
Watch the instagram video by @builtright_co (opens in new tab)

The Problem

An inside span — wall to wall, jamb to jamb — defeats a tape measure read straight: the hook sits in one corner, the case crowds the other, and the last few inches bend up the far side where you can't read them. Guessing at the bend is how trim comes up short.

The Technique

  1. Hook or butt the tape in one corner and mark a round, easy-to-add number partway across the span — 30" in the creator's demo.
  2. Pull the tape from the opposite side to that same mark and read it — here, 25-3/4".
  3. Add the two: 30 + 25-3/4 = 55-3/4". That's the exact inside span.

Picking a round number for the first mark is the whole trick — the addition happens in your head with no fraction-on-fraction arithmetic.

Pro tip: For finish work, cut a hair under the number: trim needs room to expand and contract, and a piece cut dead-on to the span goes in tight in summer and buckles a joint by winter.
Watch the instagram video by @builtright_co (opens in new tab)

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