How do I calculate the length of skirting board I need?

Add up the total perimeter of the room (all four wall lengths for a rectangular room), then subtract the width of each door opening. This gives the net run of skirting required. Add a waste allowance of 10 to 15 percent to cover angled cuts, joins, and any mistakes. For example, a 4 m x 3.5 m room has a perimeter of 15 m. With one standard 900 mm door, the net skirting run is 15 m minus 0.9 m, giving 14.1 m. Adding 10 percent waste gives 15.51 m to purchase.

How do I calculate how much architrave I need?

Architrave frames the door opening on both faces of the wall. For each door opening you need two sets of architrave: one on the room side and one on the hallway or other room side. Each set consists of two vertical legs (each equal to the door height) and one horizontal head piece (equal to the door width). So the formula per door is: (2 x door height + door width) x 2 faces. For a standard NZ door of 2040 mm tall and 900 mm wide, one door needs (2 x 2.040 + 0.900) x 2 = 9.96 m of architrave, plus waste.

What waste allowance should I add for skirting and architrave?

A 10 percent waste allowance is standard for straightforward rectangular rooms with simple butt or mitre joins. Increase to 15 percent for rooms with multiple internal corners, bay windows, or complex shapes. For architrave, 10 percent is usually sufficient because the pieces are relatively long and straight. Always round up to the next available standard length when buying from a timber merchant, as skirting is typically sold in 4.8 m or 5.4 m lengths.

Skirting and Architrave Length Calculator

This calculator works out how many linear metres of skirting board and door architrave you need for a room, so you order enough timber without running short or overspending on offcuts. Enter your room length and width, the number of doors, and a waste allowance to cover angled cuts and mitred joins. For the doors, pick a standard opening width and height from the dropdowns, or enter custom measurements, and choose whether architrave is fitted to both faces of the wall or one face only. It subtracts each door opening from the room perimeter to give the net skirting run, then adds waste for the skirting total to purchase. For architrave, it works out the two vertical legs and horizontal head piece needed per door face, multiplies by the number of doors and faces, and adds waste for the architrave total. Results show the linear metres of skirting board and architrave required including waste, the net runs before waste, and a breakdown of the perimeter, door deductions and architrave sets used. Use it when pricing a renovation, ordering materials for a new build, or checking a supplier quote, and round figures up to the nearest standard 4.8 m or 5.4 m length sold by timber merchants. These are indicative quantities only, as actual requirements depend on room shape, moulding profile and cutting skill, so confirm measurements on site before ordering.

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Standard method Perimeter minus door openings for skirting; (2 x door height + door width) x 2 faces for architrave.

1. Room Dimensions

Room length (m)

Room width (m)

Number of doors in this room

Waste allowance

2. Door Size

Door width (opening) (mm)

Custom door width (mm)

Door height (opening) (mm)

Custom door height (mm)

Architrave fitted on

Linear Metres Required

Skirting Board
15.50 m
Linear metres (inc. waste)

Door Architrave
10.98 m
Linear metres (inc. waste)

Net Skirting Run

14.09 m

Before waste

Net Architrave Run

9.98 m

Before waste

Skirting Breakdown

Room perimeter15.00 m

Number of doors1

Door opening width (each)910 mm (0.910 m)

Total deduction for doors0.910 m

Net skirting run14.09 m

Waste allowance10% (1.41 m)

Skirting to purchase15.50 m

Architrave Breakdown

Door height (opening)2040 mm (2.040 m)

Door width (opening)910 mm (0.910 m)

Architrave per set (2 legs + head)4.990 m

Faces per door2 (both faces)

Architrave per door9.980 m

Number of doors1

Net architrave run9.98 m

Waste allowance10% (1.00 m)

Architrave to purchase10.98 m

Tip: Enter your room dimensions above to see the result.

How to Measure Skirting Board

Skirting board runs along the base of every wall in a room. To find the total length required, measure the perimeter of the room (the sum of all wall lengths) and subtract the width of each door opening, since skirting does not run across doorways. Add a waste allowance to cover mitred corners, joining short offcuts, and any cutting errors.

For a rectangular room this is simply: skirting = (2 x length + 2 x width) - (number of doors x door width). Add the waste percentage to get your purchase quantity.

How to Measure Door Architrave

Architrave is the moulding that frames a door opening on each side of the wall. For a standard wall with a door, you need architrave on both the room side and the hallway (or other room) side. Each set of architrave for one face of a door consists of two vertical legs running up the sides of the opening and one horizontal head piece across the top. The formula for one set is:

2 vertical legs: 2 x door height (in metres)
1 head piece: door width (in metres)
Total per set: 2 x door height + door width

For both faces of the wall, multiply by 2. So the full architrave for one standard door (2040 mm tall x 910 mm wide, both faces) is: (2 x 2.040 + 0.910) x 2 = 9.98 m before waste.

Standard Door Sizes in New Zealand

Door Type	Width (opening)	Height (opening)
Standard bathroom / laundry	760 mm	2040 mm
Standard interior door	860 to 910 mm	2040 mm
Wide interior / accessible	960 to 1000 mm	2040 mm
Tall door (modern builds)	910 mm	2100 to 2340 mm
Double / cavity slider	1200 to 1800 mm	2040 mm

Worked Example

A bedroom measures 4.0 m x 3.5 m with one standard door (910 mm wide, 2040 mm tall), both faces architraved, and 10% waste:

Room perimeter: (2 x 4.0) + (2 x 3.5) = 15.0 m
Deduct door opening: 15.0 - 0.91 = 14.09 m net skirting
Skirting with 10% waste: 14.09 x 1.10 = 15.50 m to purchase
Architrave per set: (2 x 2.040) + 0.910 = 4.99 m
Both faces, one door: 4.99 x 2 = 9.98 m net architrave
Architrave with 10% waste: 9.98 x 1.10 = 10.98 m to purchase

These figures match the calculator defaults above.

Tips for Buying Skirting and Architrave

Timber merchants sell skirting in standard lengths of 4.8 m or 5.4 m. Round your purchase quantity up to the next full length to avoid unnecessary joins.
If running skirting in MDF, allow for expansion gaps at external walls where moisture levels may vary.
Buy a little extra architrave so you have matching material if a piece is damaged during installation.
Keep off-cuts from long lengths to fill short wall sections rather than opening a new length.
Interior corners in skirting are typically coped (not mitred) for a tighter fit over time as timber moves.

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Method: Skirting = room perimeter - (doors x door width), plus waste. Architrave = (2 x door height + door width) x faces x doors, plus waste. Standard NZ door sizes from NZS 3604 and supplier data. Waste allowances are industry convention for interior joinery.

This calculator gives indicative quantities for planning purposes. Actual requirements depend on room shape, the profile of moulding chosen, and the skill of the installer. Always check measurements on site before ordering materials.