📏 Bee Space Calculator

Bees fill gaps smaller than about 3/8 inch (0.375 in) with propolis and gaps larger than that with burr comb. Enter your box and frame measurements to check your spacing.

Box interior width (in)

Number of frames

Frame width (in, including end bars)

Slack divided by gaps

The calculator adds up the frames, sees what room is left in the box, and spreads it evenly across every gap including the two against the walls:

total frame width = frames × frame width
remaining         = box interior width - total frame width
gaps              = frames + 1
space per gap     = remaining / gaps

With the defaults - 18.5 in inside, ten frames at 1.5 in - the frames take up 15.000 in, 3.500 in is left, and eleven gaps make 0.318 in each. The verdict line compares that against 0.375 in with a tolerance of 0.125 in, so anything from 0.250 to 0.500 in reads as normal. Below the band it warns you the bees will propolise; above it, that they will draw burr comb.

Measuring the three inputs

Box interior width is wall to wall, not the outside of the box. A 10-frame Langstroth is about 18-3/8 in inside, being 19-7/8 in outside less two 3/4 in walls.
Frame width is the widest point of the end bar. Hoffman self-spacing bars are 1-3/8 in; narrow bars with metal spacers measure less.
Frame count is what is actually in the box. Running nine frames in a ten-frame box is a deliberate choice, and the tool will show you the wider gap it produces.

Real frames do not float. Pushed together, self-spacing end bars fix the gaps between frames and dump all the slack at the two walls, so treat the even split as a check on whether the box has about the right amount of room, not a prediction of any one gap.

Frequently asked questions

What is bee space in inches?

Three eighths of an inch, 0.375 in. This tool treats 0.250 to 0.500 in as the workable band, and flags anything outside it.

What is the inside width of a 10-frame Langstroth box?

About 18-3/8 in. The outside is 19-7/8 in and standard walls are 3/4 in thick, which takes an inch and a half off.

Why does the calculator use eleven gaps for ten frames?

There are nine gaps between the frames and one more at each side wall. Frames need clearance from the box as much as from each other, so the count is always one higher than the number of frames.