3D printing · Bed fit
3D print rotated fit calculator.
Enter the part’s length, width and height and your bed size, and the calculator tells you whether the part fits flat as it is, whether it fits if you turn it on the plate, and at what angle. Example: a 300 × 20 mm strip does not fit a 256 × 256 mm bed (Bambu Lab A1) square-on, but it fits turned 45°, with about 30 mm to spare. A 350 × 20 mm strip does not fit at any angle, even though the bed diagonal is 362 mm.
Your numbers
Result
Working out the result.
How the fit is calculated
Turn a rectangle of length L and width W through an angle θ on the plate and its footprint becomes (L cosθ + W sinθ) by (L sinθ + W cosθ). The part fits when that footprint is no bigger than the bed on both sides, less your clearance. The calculator tries every angle from 0° to 90° in steps of 0.05° and reports the angles that work, the one with the most spare room and, if square-on does not fit, the smallest turn that does. Height is checked separately because turning flat does not change it. The same question of when one rectangle fits inside another was posed by Ford in 1956, and “a necessary and sufficient condition on the sides was soon supplied by Carver” (J. E. Wetzel, The Mathematical Gazette 86, 2002, abstract); this tool is checked in its tests against the exact condition in the 1996 IMO shortlist solution (problem 15): with a < c ≤ d < b, an a × b rectangle fits inside a c × d one if and only if (b² − a²)² ≤ (bc − ad)² + (bd − ac)².
Bed sizes: the Bambu Lab A1 specification sheet gives 256 × 256 × 256 mm and Prusa’s MK4S page gives 250 × 210 × 220 mm (read 26 October 2026).
Worked examples with real numbers
- 300 × 20 mm strip, 256 × 256 mm bed. Square-on it is 44 mm too long. At 45° the footprint is (300 + 20) ÷ √2 = 226.3 mm each way, 29.7 mm inside the bed. It fits at any angle from about 35° to 55°.
- 350 × 20 mm strip, same bed. The bed diagonal is 362 mm, but at 45° the footprint is (350 + 20) ÷ √2 = 261.6 mm, over 256. It does not fit at any angle.
- Longest 20 mm-wide part on that bed. At 45° the limit is L + 20 = 256 × √2 = 362.0, so L = 342 mm. A 340 mm strip fits with 1.4 mm to spare per side.
- Prusa MK4S, 250 × 210 mm. The bed diagonal is 326.5 mm. A 260 × 30 mm part is 10 mm too long square-on but fits turned between about 24° and 47°.
What this calculator leaves out
It treats the part as its bounding rectangle seen from above. A part with a diagonal shape can often be turned further than its box allows, and a part shaped like an L wastes the corners of the box, so a slicer that places the real outline may fit parts this tool rejects. It only turns about the vertical axis; tilting a part, cutting it into pieces or printing it on its side is a different question. Bed edges are rarely fully usable, so use the clearance field.
Common mix-ups
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Often assumedA long thin part fits if it is shorter than the bed diagonal.
What the source saysThe diagonal is the limit only for a part with no width. On a 256 × 256 mm bed a 20 mm-wide strip tops out at 342 mm, so a 350 × 20 mm strip does not fit although the diagonal is 362 mm. Width eats into the diagonal. [1]
Checked against these sources on .
Frequently asked questions
Will my part fit on the printer diagonally?
Enter its footprint and your bed size above. A part longer than the bed side can fit turned on the plate if its width is small enough: a 300 x 20 mm strip fits a 256 x 256 mm bed at 45 degrees, while a 350 x 20 mm strip does not fit at any angle.
What angle should I rotate the part?
On a square bed, 45 degrees gives the most room for a long thin part. On a rectangular bed the best angle is not 45. The calculator reports the angle with the most spare room and the range of angles that work.
What is the longest part I can print flat?
For a part with width W on a square bed of side S, the limit at 45 degrees is L = S x 1.414 minus W. For a 20 mm width on a 256 mm bed that is 342 mm, not the 362 mm bed diagonal.
Does rotating change the height I need?
No. This tool turns the part about the vertical axis, so the Z height stays the same.
Why does my slicer fit a part this says will not fit?
This tool uses the bounding box of the part. A slicer that arranges the true outline can use the empty corners of that box.
Does clearance matter?
Yes. Skirts, brims and purge lines need room, and the edges of a bed are often unusable. Enter the margin you need on each side.
Sources
Retrieved
- 37th IMO 1996 shortlist, problem 15 solution — exact condition for one rectangle to fit inside another, used to test this tool (read 2026-10-26)
- J. E. Wetzel, Squares in triangles, The Mathematical Gazette 86 (2002), abstract — Ford asked in 1956 when one rectangle fits in another; a condition was soon supplied by Carver (read 2026-10-26)
- Bambu Lab: A1 specification sheet — build volume 256 x 256 x 256 mm (read 2026-10-26)
- Prusa3D: Original Prusa MK4S — build volume 250 x 210 x 220 mm (read 2026-10-26)
Bounding-box fit only
Not affiliated with Bambu Lab or Prusa Research. The check uses the part’s bounding rectangle, so a slicer that places the real outline may fit more. Nothing you type is sent or stored.