How the Stud Hole & Notch Checker works
Check the hole or notch you are about to cut in a wall stud against the 2021 IRC limits, and see the largest size that passes, before you pick up the drill.
How this is calculated
The residential code limits how much wood you may take out of a wall stud as a share of the stud's depth, the wide dimension that a pipe or cable passes through. This tool applies Section R602.6 of the 2021 IRC to the stud you describe. The rules, in plain words:
- Notches. In an exterior wall or a bearing partition, a notch may be no deeper than 25% of the stud depth. In an interior nonbearing partition, no deeper than 40% of the depth of a single stud.
- Bored holes. No hole in any stud may be wider than 60% of the stud depth. In an exterior wall or a bearing partition, a hole over 40% is only allowed where the stud is doubled, and no more than 2 doubled studs in a row may be bored that way.
- Edge distance. The rim of a hole must be at least 5/8 in from the edge of the stud.
- Hole and notch. A hole may not be in the same section of the stud as a cut or notch. The code figures call it the same cross section.
deepest notch = stud depth × 25% (exterior or bearing wall)
= stud depth × 40% (nonbearing partition)
largest hole = stud depth × 40% (single stud, exterior or bearing wall)
= stud depth × 60% (doubled stud there, or any nonbearing partition)
and never more than stud depth − 2 × 5/8 inFor the standard stud sizes that works out as below. Fractions are rounded down to the 1/16 in at or under the exact figure, which is shown in brackets.
| Stud | Hole, bearing, single | Hole, bearing, doubled | Notch, bearing | Hole, nonbearing | Notch, nonbearing |
|---|---|---|---|---|---|
| 2x4 (3 1/2") | 1 3/8" (1.4") | 2 1/16" (2.1") | 7/8" (0.875") | 2 1/16" (2.1") | 1 3/8" (1.4") |
| 2x6 (5 1/2") | 2 3/16" (2.2") | 3 1/4" (3.3") | 1 3/8" (1.375") | 3 1/4" (3.3") | 2 3/16" (2.2") |
| 2x8 (7 1/4") | 2 7/8" (2.9") | 4 5/16" (4.35") | 1 13/16" (1.8125") | 4 5/16" (4.35") | 2 7/8" (2.9") |
Two of the handouts read for this tool round some hole sizes up to a tape fraction instead. They show 1 7/16 in for a 2x4 bearing stud and 2 1/8 in for a 2x4 partition stud, and one shows 3 5/16 in for a 2x6 partition stud. Those are a little over 40% and 60% of the stud depth, so this tool reports them as failing and gives the next sixteenth down.
How this tool reads the wording:
- Edge distance, both sides. The text names the edge of the stud and each code figure dimensions one side. This tool checks the 5/8 in against both edges: whichever side you measure, the smaller strip of wood is the one compared with 5/8 in. That is the stricter reading, and it is why the largest hole is also capped at the stud depth less 1 1/4 in.
- Same section means same height. Figures R602.6(1) and R602.6(2) word the rule as a hole not being in the same cross section of the stud as a cut or notch, and neither the text nor the figures give a spacing. This tool reads that as the same height: if a level line across the stud would touch both, they share a section and the check fails. A hole just above or below a notch passes this check, which is the plain reading and not a cautious one, so ask your inspector when they are close. The only cautious part is the default: the tool assumes the same height until you say otherwise.
- Exterior walls. Any exterior wall gets the bearing-wall limits, because the section groups exterior walls with bearing partitions. The 60% hole and 40% notch are for interior nonbearing partitions only.
- Doubled studs. Doubling raises the hole limit only; the notch limits stay the same. The section says the stud must be doubled but not how, so this tool takes your word that it is and does not describe a way to do it. The count of doubled studs in a row covers every doubled stud bored over 40%, not only holes of the same size.
The section also has an exception for approved stud shoes installed to the manufacturer's instructions. That depends on the product and on your building department, so it is not calculated here.
What the tested examples show. Only two of the sources print inch figures for a particular stud, both handouts. Every figure of theirs that is at the exact percentage, or is the sixteenth just under it, is used below as a published example and compared with what the calculator computes: four notch depths, one hole size, and one worked 25%. Three of the six equal 25% exactly; the other three are the sixteenth below 40% and are compared with the calculator's rounded-down figure. No source read for this tool prints a worked pass or fail for a given hole, an edge-distance case or a doubled-stud case with numbers. Those examples, and the exact decimal maximums, are worked by hand from the 2021 IRC text and its two figures and are marked that way.
Scope. Solid sawn wood studs in conventional light-frame walls, under the 2021 IRC, one hole and one notch at a time. The section says nothing about two holes side by side across the depth of a stud or about spacing between holes up the stud, so this tool does not check either. The 2015, 2018 and 2024 texts read for this tool give the same percentages and the same 5/8 in; older editions say "stud width" where newer ones say "stud depth". The two sources disagree about how the older editions printed the 5/8 in: the ICC proposal says the earlier text had it as a maximum by mistake, while the 2015 and 2018 pages read for this tool show a minimum. The 2021 IRC wording is a minimum, which is what this tool checks. Your jurisdiction may have adopted a different edition or amended it.
This tool does not cover top plates (R602.6.1), headers, joists, rafters, steel studs or engineered studs, and it is not an engineering review of the wall. It also does not check the separate rules for protecting pipes and cables that run close to the edge of a stud. For piping in concealed locations, other than cast-iron or galvanized steel pipe, Section P2603.2.1 calls for steel shield plates where the hole or notch is less than 1 1/4 in from the nearest edge of the stud, so a hole that passes here can still need them. Stud depths for 2x4, 2x6 and 2x8 are the dressed dry sizes in the American Softwood Lumber Standard; measure older or rough-sawn lumber and enter it under Other.
What this calculator is tested against
This tool cannot be published unless it reproduces every example below. 6 are copied from a published source. 18 were worked by hand from the cited rule.
| Example | Expected | Basis |
|---|---|---|
| 2x4 stud, exterior or bearing wall: deepest notch | 7/8 in | Published City of Richmond, KY, Cutting, Drilling, and Notching (2018 Kentucky Residential Code R602.6) |
| 2x6 stud, exterior or bearing wall: deepest notch | 1 3/8 in | Published City of Richmond, KY, Cutting, Drilling, and Notching (2018 Kentucky Residential Code R602.6) |
| 25% of a 3 1/2 in stud, as worked in the WWPA guide | 0.875 in, which is 7/8 in | Published WWPA Notching & Boring Guide, footnote to Figures 2 and 3 |
| 2x4 stud, nonbearing partition: deepest notch to the sixteenth below 40% | 1 3/8 in | Published City of Richmond, KY, Cutting, Drilling, and Notching (2018 Kentucky Residential Code R602.6) |
| 2x6 stud, nonbearing partition: deepest notch to the sixteenth below 40% | 2 3/16 in | Published City of Richmond, KY, Cutting, Drilling, and Notching (2018 Kentucky Residential Code R602.6) |
| 2x6 stud, exterior or bearing wall: largest hole to the sixteenth below 40%, drilled centred | 2 3/16 in is the largest hole listed, and a hole that size passes | Published City of Richmond, KY, Cutting, Drilling, and Notching (2018 Kentucky Residential Code R602.6) |
| 1 7/16 in hole in a single 2x4 bearing stud (the size two handouts print as the maximum) | 41.1% of 3.5 in, over 40% — fails; 1 3/8 in is the largest sixteenth that passes | By hand 2021 IRC R602.6 item 2 and Figure R602.6(1), exterior and bearing walls |
| 2 1/8 in hole in a 2x4 nonbearing stud (the size two handouts print as the maximum) | 60.7% of 3.5 in, over 60% — fails; 2 1/16 in is the largest sixteenth that passes | By hand 2021 IRC R602.6 item 2 and Figure R602.6(2), interior nonbearing walls |
| 3 5/16 in hole in a 2x6 nonbearing stud (the size one handout prints as the maximum) | 60.2% of 5.5 in, over 60% — fails; 3 1/4 in is the largest sixteenth that passes | By hand 2021 IRC R602.6 item 2 and Figure R602.6(2), interior nonbearing walls |
| 2x4 stud in a bearing wall: largest hole, single and doubled | 1.4 in single (40% of 3.5), 2.1 in doubled (60% of 3.5) | By hand 2021 IRC R602.6 item 2 and Figure R602.6(1), exterior and bearing walls |
| 2x4 stud in a nonbearing partition: largest hole and deepest notch | hole 2.1 in (60% of 3.5), notch 1.4 in (40% of 3.5) | By hand 2021 IRC R602.6 items 1 and 2 and Figure R602.6(2) |
| 2x6 stud in a bearing wall: largest hole, single and doubled | 2.2 in single (40% of 5.5), 3.3 in doubled (60% of 5.5) | By hand 2021 IRC R602.6 item 2 and Figure R602.6(1), exterior and bearing walls |
| 2x6 stud in a nonbearing partition: largest hole and deepest notch | hole 3.3 in (60% of 5.5), notch 2.2 in (40% of 5.5) | By hand 2021 IRC R602.6 items 1 and 2 and Figure R602.6(2) |
| 2x3 stud in a nonbearing partition: the 5/8 in edge rule governs | 1 1/4 in (2.5 − 2 × 5/8), less than 60% of 2.5 = 1.5 in | By hand 2021 IRC R602.6 item 2 (boring) |
| 1.4 in hole centred in a single 2x4 bearing stud | exactly 40% — passes, 1.05 in left each side | By hand 2021 IRC R602.6 item 2 and Figure R602.6(1), exterior and bearing walls |
| 1 7/16 in hole with the 2x4 bearing stud doubled, two doubled studs in a row bored | between 40% and 60%, doubled, two in a row — passes | By hand 2021 IRC R602.6 item 2 and Figure R602.6(1), exterior and bearing walls |
| Three doubled 2x4 bearing studs in a row, each bored 2 in | more than two successive doubled studs bored over 40% — fails | By hand 2021 IRC R602.6 item 2 and Figure R602.6(1), exterior and bearing walls |
| 1.4 in hole in a single 2x3 bearing stud | 56% of 2.5 in — fails, and doubling would not help: only 0.55 in is left each side | By hand 2021 IRC R602.6 item 2 and Figure R602.6(1), exterior and bearing walls |
| 1 1/2 in hole in a 2x6 bearing stud, hole edge 5/8 in from the stud edge | exactly at the 5/8 in minimum — passes | By hand 2021 IRC R602.6 item 2 (boring) |
| The same hole 9/16 in from the stud edge | 1/16 in too close to the edge — fails | By hand 2021 IRC R602.6 item 2 (boring) |
| 2 1/4 in hole centred in a 2x4 nonbearing stud | keeps 5/8 in each side but is 64.3% of the depth — over 60%, fails | By hand 2021 IRC R602.6 item 2 and Figure R602.6(2), interior nonbearing walls |
| 7/8 in notch in a 2x4 bearing stud | exactly 25% — passes | By hand 2021 IRC R602.6 item 1 (notching) |
| 15/16 in notch in a 2x4 bearing stud | 26.8% — over 25%, fails | By hand 2021 IRC R602.6 item 1 (notching) |
| 1 in hole and 3/4 in notch in the same cross section of a 2x4 bearing stud | each is small enough on its own, but a hole may not share a cross section with a notch — fails | By hand 2021 IRC R602.6 item 2 and Figure R602.6(1), exterior and bearing walls |
Sources
- 2021 International Residential Code, Section R602.6 and Figures R602.6(1) and R602.6(2)Read on UpCodes, a third-party reproduction, on its page titled Texas IHB Residential Code 2021 (which adopts the 2021 IRC with amendments; this section carries no amendment flag). Every limit used here comes from this text and its two figures. The 2015, 2018 and 2024 pages on the same site were read too and give the same percentages and the same 5/8 in. Those 2015 and 2018 pages print the 5/8 in as a minimum; the ICC proposal listed next says the text of that time printed it as a maximum by mistake. The 2021 wording, a minimum, is what this tool checks.
- ICC code change proposal IRC 6-1, Notching and boring clarificationsAn International Code Council proposal to reword R602.6, from the Group B 2019 cycle. The file does not name an edition or say it was adopted, and its strike-through marks are not in the text, so it is used for one thing only: its stated reasons. They say that "depth" replaces "width", that permissive wording becomes mandatory, and that the earlier printed text had the 5/8 in clause the wrong way round, as a maximum where a minimum was meant. It states no limits other than 25, 40 and 60 percent and 5/8 in (16 mm), and the 2021 section read on UpCodes uses the reworded form.
- City of Richmond, Kentucky: Cutting, Drilling, and Notching (2018 Kentucky Residential Code)Prints maximum notch depths and hole sizes for 2x4 and 2x6 studs. Its four notch depths and its 2x6 bearing-wall hole (2 3/16 in) are at or just under the exact percentages and are used as tested examples: the two bearing-wall notches (7/8 in and 1 3/8 in) equal 25% exactly, and the other three are the sixteenth below 40% of the stud depth. Its other three hole sizes (1 7/16 in for a 2x4 bearing stud, 2 1/8 in and 3 5/16 in for 2x4 and 2x6 nonbearing studs) are slightly over 40% or 60% of the stud depth; this tool fails those sizes.
- WWPA Notching & Boring Guide for Floor Joists & Stud WallsWestern Wood Products Association tip sheet dated 1996-97, written for the model codes that came before the IRC (UBC, SBC, BOCA and CABO); it notes that BOCA allowed a hole of one third of the stud in all cases. It shows 25%, 40% and 60% on a 3 1/2 in stud, says the percentages apply to studs of any size, and works 25% of 3 1/2 in as 7/8 in, which is used as a tested example.
- MyBuildingPermit Tip Sheet 11, Notching & Boring (2012 codes)Jurisdiction handout summarising R602.6 under the 2012 codes with the same 25%, 40% and 60% limits and the 5/8 in edge distance. Read for comparison only; no tested example relies on it.
- American Softwood Lumber Standard, PS 20-20 Revision 1 (NIST, 2021), Table 3Minimum dressed dry widths of dimension lumber: nominal 4 in = 3 1/2 in, 6 in = 5 1/2 in, 8 in = 7 1/4 in. These are the stud depths behind the 2x4, 2x6 and 2x8 buttons.
- 2021 International Residential Code, Section P2603.2.1, Protection against physical damageNot checked by this tool; read only to state its scope. In concealed locations, where piping other than cast-iron or galvanized steel runs through a hole or notch less than 1 1/4 in from the nearest edge of a stud, this separate section calls for steel shield plates, so a hole that passes here at 5/8 in can still need them.