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How To Calculate Lumber For Framing
Framing a wall comes down to counting studs at a fixed spacing, adding the plates that tie them together, and buying a little extra for the cuts that go wrong.
Quick Answer
n = ceil(L / s) + 1
- L
- Wall length, in metres
- s
- Stud spacing, in metres once converted from millimetres
- n
- Number of studs, including both ends
- h
- Wall height, which sets the length of each stud
- w
- Waste allowance as a decimal
Divide the wall length by the stud spacing, round up, and add one for the end stud. A 6 metre wall at 600 millimetre spacing needs 10 spaces, so 11 studs, plus 2 more for a single opening, giving 13 studs and 18 metres of plate. With a ten percent allowance the wall takes about 54.12 metres of timber.
What Is Lumber For Framing?
Framing lumber is counted in two parts: the vertical studs that carry the load and the horizontal plates that hold them in position. The stud count follows from the wall length and the spacing between studs, and the plate length is simply the wall length multiplied by the number of runs. Together they give the linear metres of timber to buy.
Stud spacing is quoted in millimetres because that is how building regulations and timber merchants describe it, while wall lengths are measured in metres. Converting the spacing to metres, or the length to millimetres, is the first thing to get straight. Six metres is six thousand millimetres, which is ten spaces at six hundred millimetres.
The number of studs is one more than the number of spaces, because both ends of the wall need a stud. A wall with ten spaces between studs therefore has eleven studs. This off-by-one is the most common counting error in framing, and it is invisible until the last bay comes up short.
A standard wall has three plate runs: a single bottom plate that the studs sit on, and a double top plate that ties the wall together and laps at corners. The double top plate is what makes the wall stiff and what carries the floor or roof above it. Plate length is therefore the wall length multiplied by three.
Openings for doors and windows need extra framing. Each opening takes a stud on either side to carry the trimmer, and a header spans the gap above. Counting two extra studs per opening is a reasonable first approximation for the vertical timber; the header is usually cut from stock of a heavier section.
Stud length is not the same as wall height. The studs sit between the bottom plate and the top plate, so each one is cut to the wall height minus the thickness of the plates. With 45 millimetre plates top and bottom, a 2.4 metre wall takes studs cut to about 2.31 metres.
Spacing is chosen to suit the sheathing and the loads. Six hundred millimetres suits most sheet materials and is the economical choice for non-load-bearing partitions, while four hundred millimetres gives a stiffer wall and is common where cladding is fixed directly or where the wall carries a heavy load above.
Converting stud count into linear metres is what the timber yard actually sells. Multiplying the stud count by the stud length gives the vertical timber, and adding the plate runs gives the total. A wall of thirteen studs at 2.4 metres plus 18 metres of plate comes to just over 49 metres before any allowance.
A waste allowance covers the timber lost to cutting and to defects. Ten percent is a sensible default for a single wall framed by hand, because boards arrive with knots and slight bows and the first cut on each board often removes a damaged end. Buying exactly the calculated length guarantees a second trip.
The calculation assumes a straight, single-storey wall with no bracing, no blocking and no doubled studs at corners. Those details are added on top, and for a whole building the bracing and the corner assemblies can add a meaningful amount of timber to the total.
Formula
n = ceil(L / s) + 1
Divides the wall length by the spacing, rounds up to a whole number of spaces, then adds the stud at the far end. Both ends of a wall need a stud.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| L | Wall length | metres | Measured along the wall, in metres. |
| s | Stud spacing | metres | Centre to centre, converted from millimetres to metres. |
| n | Stud count | studs | Spaces plus one, plus any studs added for openings. |
P = 3 L
One bottom plate and a double top plate make three runs along the wall. The double top plate stiffens the wall and laps at corners.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| L | Wall length | metres | The same length used for the stud count. |
| P | Plate length | metres | Three runs, so three times the wall length. |
T = (n h + P) (1 + w)
Adds the vertical timber to the plates and then applies the waste allowance. The result is the linear metres of timber to buy.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| n | Stud count | studs | Including studs added for openings. |
| h | Stud length | metres | Wall height less the plate thicknesses. |
| P | Plate length | metres | Three runs along the wall. |
| w | Waste allowance | dimensionless | A decimal, so ten percent is 0.1. |
| T | Total timber | metres | Linear metres to order. |
How To Calculate Lumber For Framing
- 1
Measure the wall length
Measure along the wall rather than between finished surfaces, because the plates run the full length and lap at the corners. Record the figure in metres and keep it consistent with the spacing unit you use next.
- 2
Divide by the stud spacing
Six metres divided by six hundred millimetres is ten spaces, provided both are in the same unit. Using metres for the wall and millimetres for the spacing turns a ten space wall into a ten thousand space wall.
- 3
Round up and add one
Round the number of spaces up to a whole number, then add one for the stud at the far end. Ten spaces give eleven studs. Skipping the plus one leaves the wall one stud short at the end.
- 4
Add two studs per opening
Every door or window needs a stud on each side to carry the trimmer and the header. Count the openings and add two studs each, then add the headers separately from heavier stock.
- 5
Add the plates and the waste allowance
Multiply the wall length by three for the plates, multiply the stud count by the stud length, add the two together, and apply the waste allowance. A ten percent allowance is the usual figure for a hand-framed wall.
Examples
Example 1: A 6 metre wall at 600 mm spacing
- Wall length
- 6 metres
- Stud spacing
- 600 millimetres
- Wall height
- 2.4 metres
- Openings
- none
- Waste
- 10 percent
| Step | Calculation | Result |
|---|---|---|
| Number of spaces | 6000 / 600 | 10 |
| Studs including the end stud | 10 + 1 | 11 |
| Vertical timber | 11 x 2.4 | 26.4 |
| Plate runs | 6 x 3 | 18 |
| Total with waste | (26.4 + 18) x 1.1 | 48.84 |
Result: The wall takes 11 studs and 18 metres of plate, so with a ten percent allowance the timber order is 48.84 linear metres in total.
Example 2: The same wall with one opening at 400 mm spacing
- Wall length
- 6 metres
- Stud spacing
- 400 millimetres
- Wall height
- 2.4 metres
- Openings
- one door
- Waste
- 10 percent
| Step | Calculation | Result |
|---|---|---|
| Number of spaces | 6000 / 400 | 15 |
| Studs including the end stud | 15 + 1 | 16 |
| Studs with the door opening | 16 + 2 | 18 |
| Vertical timber | 18 x 2.4 | 43.2 |
| Plate runs | 6 x 3 | 18 |
| Total with waste | (43.2 + 18) x 1.1 | 67.32 |
Result: Tightening the spacing to 400 millimetres and adding one door opening gives 18 studs and 43.2 metres of vertical timber, so the order rises to 67.32 linear metres.
Example 3: What tighter spacing costs
- Wall length
- 6 metres
- Coarse spacing
- 600 millimetres
- Fine spacing
- 400 millimetres
- Stud length
- 2.4 metres
| Step | Calculation | Result |
|---|---|---|
| Studs at 600 millimetres | 6000 / 600 + 1 | 11 |
| Studs at 400 millimetres | 6000 / 400 + 1 | 16 |
| Extra studs | 16 - 11 | 5 |
| Extra timber | 5 x 2.4 | 12 |
Result: Dropping the spacing from 600 to 400 millimetres adds 5 studs to a 6 metre wall, which is 12 extra metres of stud timber on that wall alone.
Calculator
Studs required
13
- Plate length in metres
- 18
- Stud timber in metres
- 31.2
- Total timber in metres
- 54.12
Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.
Prefer a full-width tool? Open the Lumber For Framing calculator page.
Common Mistakes
Forgetting the stud at the far end
The number of studs is the number of spaces plus one, because both ends of the wall are framed. Counting spaces alone leaves the final bay unsupported, and the gap is only noticed when the sheathing is fixed.
Treating the plates as a single run
A standard wall has one bottom plate and a double top plate, which is three runs in total. Counting a single top plate understates the plate timber by a third, and the wall loses the stiffness the second plate provides.
Ignoring openings
Every door and window needs a stud on each side to carry the trimmer, plus a header above. Ignoring them means the openings are framed from studs that were allocated to the wall, and the wall runs short by exactly that amount.
Mixing metres and millimetres
Wall lengths come in metres and stud spacings in millimetres. Dividing one by the other without converting produces a stud count that is out by a factor of a thousand, which is immediately obvious in the total but easy to miss in the individual steps.
Rounding the stud count down
The number of spaces must be rounded up, not to the nearest whole number. Rounding 10.5 spaces down to 10 leaves a final bay wider than the sheathing can span, and the wall will not be square when the sheets go on.
Cutting studs to the full wall height
Studs sit between the plates, so each one is shorter than the wall by the thickness of the bottom and top plates. Cutting to the full height means the wall ends up taller than planned and the plates no longer line up with the rest of the frame.
FAQ
How many studs do I need for a wall?
Divide the wall length by the stud spacing, round up to a whole number of spaces, and add one for the far end. A 6 metre wall at 600 millimetre spacing has 10 spaces and therefore 11 studs, plus two more for each door or window opening.
Should I use 400 or 600 millimetre spacing?
Six hundred millimetres suits most sheet materials and is the economical choice for internal partitions. Four hundred millimetres gives a stiffer wall, which matters where cladding is fixed directly to the frame, where the wall carries a heavy load, or where the sheathing needs extra support.
How much extra lumber should I buy?
Ten percent is a reasonable allowance for a wall framed by hand, covering cutting losses and the defects at the ends of boards. Add more where the frame is complicated, and remember that buying exactly the calculated length guarantees a second trip to the yard.
What are plates in framing?
Plates are the horizontal members that run along the top and bottom of a wall. The bottom plate is a single run the studs stand on; the top plate is doubled, so the wall has three plate runs in total. The double top plate ties the wall together and laps at corners.
Do I need to add studs for doors and windows?
Yes. Each opening takes a stud on either side to support the trimmer and to give the header something to bear on. Two extra studs per opening is a good first estimate for the vertical timber, with the header itself cut from heavier stock.
How long should each stud be?
Wall height minus the thickness of the plates the stud sits between. For a 2.4 metre wall framed with 45 millimetre plates top and bottom, the studs are cut to about 2.31 metres. Cutting to the full wall height makes the finished wall taller than the rest of the frame.
References
- [1]Wikipedia, Framing (construction) — https://en.wikipedia.org/wiki/Framing_(construction)
- [2]Wikipedia, Wall stud — https://en.wikipedia.org/wiki/Wall_stud
- [3]Wikipedia, Lumber — https://en.wikipedia.org/wiki/Lumber