SettingsSettings for this calculationUS
Waste is set to 5% by hand. Pick a tier above to replace it, or keep your own figure.
The floor framing's overall length.
The long dimension of the framed floor, measured outside to outside of the framing. Rim board runs the whole perimeter, so this and the width together give the run — but only the two ends carry rim board where the joists bear; the other two sides carry it against the joist ends. Both are included, which is why the perimeter rather than one dimension is what the material follows.
The floor framing's overall width.
The other outside dimension of the framing. Take it at the framing rather than at the finished wall: a floor inside a masonry cavity wall is smaller than the building, and rim board follows the timber. Where the floor is not rectangular, work it as rectangles and add the perimeters, deducting the joins.
Extra material to allow for cutting waste and seams at corners.
Rim board is supplied in long lengths and used in long runs, so the waste is mostly the end of the last piece on each side plus the corner joins — typically modest, and lower than a sheet material's allowance. Raise it if the floor has many corners or steps, because each one is another cut and another short offcut nobody will find a use for.
Rim board needed
123.9 ft
- Perimeter (no waste)
- 118 ft
They open the calculator with your figures already in it
Rim Board Linear Footage Calculator: 124 ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Rim board runs the full perimeter of the floor framing at each level; total length = perimeter × (1 + waste factor)
Inputs used
- Building Length
- 33 ft
- Building Width
- 26 ft
- Waste Allowance (%)
- 5
Intermediate steps
- Perimeter (no waste)
- 118 ft
What this calculation does not cover
- Assumes the floor is a plain rectangle. A bay, a bump-out, a stepped footprint or an L-shaped plan all have a longer perimeter than twice length plus width, and a cantilevered section puts the rim at the cantilever line rather than at the wall below it. Two dimensions cannot describe those, and the shortfall turns up on site as a run with no board left for it.
- Says nothing about which board. The same metres are satisfied by a 25 mm (1 in) OSB rim and by a 45 mm (1.8 in) LSL rim of identical depth, and the choice is set by the vertical load coming down from the wall above — the rim is the bearing under that wall for the whole thickness of the joist zone. Ordering the length right in the wrong product gives a rim that crushes under the load path the drawing assumed it would carry.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Rim board runs the full perimeter of the floor framing at each level; total length = perimeter × (1 + waste factor)
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