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Tool Belt Calc

Home improvement

Baseboard Calculator

Linear feet of baseboard, and how many lengths that is.

Your measurementsEvery assumption editable01

Add up the width of every opening with no skirting across it.

Covers mitres at corners and the short offcuts they leave.

Trim requiredCalculated live02

Result

6lengths

6 × 8 ft lengths

Room perimeter
48 ft
Less doorways
−6 ft
Net run to cover
42 ft
With waste allowance+10%
46.2 ft
Lengths to buy
6 × 8 ft
Total supplied6 ft spare
48 ft

Buy lengths that suit the walls rather than the total. A 12 ft wall needs a 12 ft length or a visible joint, and no amount of extra 8 ft stock will fix that — count your longest walls before ordering.

Mitred internal corners waste more than you expect, and the offcut from a 45 degree cut is rarely usable at the next corner. Ten per cent is a floor for a room with several corners.

The same calculation works for crown moulding, picture rail and dado rail. Crown is harder to cut and worth a higher waste allowance on a first attempt.

Enter the room perimeter, subtract the doorways, and it returns the run to cover along with the number of lengths to buy. The same calculation works for crown moulding, picture rail and dado rail.

Why use this tool?What it does differently03

Why use this tool?

Doorways deducted

Openings with no trim across them come off the perimeter, which on a room with two doors is several feet.

Answers in lengths

Trim is sold in fixed lengths, so linear feet is converted to the number of pieces at the length you are buying.

Spare shown

How much surplus the rounding leaves, which tells you whether you have enough for a mistake.

Works for any trim

Baseboard, skirting, crown, picture rail and dado all follow the same perimeter arithmetic.

How this worksThe method04

How this baseboard calculator works

The run to cover is the room perimeter less the total width of any doorways that have no trim across them. That figure is uplifted by the waste allowance and divided by the length of trim you are buying.

The waste allowance covers mitres. A 45 degree internal corner leaves an offcut that is rarely usable at the next corner, and a room with six corners generates six of them. Ten per cent is a floor rather than a generous margin.

The spare figure matters more here than for most materials, because trim is the last thing to go on and a bad cut at that stage is disproportionately annoying. Having a length in hand is worth the small extra cost.

How to use itStep by step05

How to use it

  1. Step 1: Measure the perimeter

    Around the base of every wall in the room, including behind where furniture will sit.

  2. Step 2: Add up the doorways

    The total width of openings that have no trim running across them. Cased openings without a threshold still break the run.

  3. Step 3: Check your longest wall

    Before choosing a length to buy, note the longest single wall. A 12 foot wall needs a 12 foot length or it shows a joint.

  4. Step 4: Allow for mitres

    Ten per cent minimum, more for a room with many corners or if this is your first time cutting crown.

Example usageWorked figures06

Example usage

A standard bedroom
A 48 foot perimeter less 6 feet of doorways is 42 feet, 46.2 with waste. In 8 foot lengths that is 6 pieces supplying 48 feet — under 2 feet spare, which is tight.
Buying longer stock
The same room in 12 foot lengths needs 4 pieces supplying 48 feet. Same total, but far fewer joints on the long walls.
Crown moulding first attempt
Identical perimeter arithmetic, but raise the waste to 20%. Crown is cut at compound angles and the first few attempts usually end up in the offcut pile.
Frequently asked questionsCommon questions07

Frequently asked questions

How much baseboard do I need?

Room perimeter less the doorway widths, plus about 10 per cent for mitre waste. A 48 foot perimeter room with 6 feet of doorways needs roughly 46 linear feet.

What length should I buy?

Long enough to run your longest wall in one piece. A joint mid-wall is visible however well it is scarfed, and no amount of extra short stock will fix a wall that exceeds the length you bought.

How much waste for mitred corners?

Ten per cent minimum. Each 45 degree cut leaves an offcut too short to reuse, and a room with several corners generates one per corner. Twenty per cent is sensible for crown moulding or a first attempt.

Does this work for crown moulding?

Yes — the perimeter arithmetic is identical. Crown is harder to cut because the angles are compound rather than simple mitres, so use a higher waste allowance.

Should I deduct for a fireplace or built-in?

Only where the trim genuinely stops. Deduct the width of anything that breaks the run at floor level, but leave the perimeter intact where trim continues behind or around it.

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