An 8 ft ceiling with 2x12 joists (108" floor to floor) needs 14 risers at 7-11/16" and 13 treads: a 130" run on 10" treads, cut from 16 ft 2x12s with 5-1/8" of throat. Gentler: 15 risers at 7-3/16" on 11" treads, a 154" run (2R + T = 25.4").
finished to finished
fewest legal
nosing to nosing
3/4–1-1/4 under 11″
DCA 6 max 18
108" total rise
Hook the tape once at mark 0, where the bottom riser line meets the top edge of the 2x12, and pencil every mark from that same hook. Each step is 12-5/8" along the edge; marks are rounded once each, so nothing drifts.
| Done | # | Mark | Tape | Decimal | mm |
|---|---|---|---|---|---|
| 0 | Bottom riser line | 0" | 0.000" | 0 mm | |
| 1 | Tread 1 nose | 12-5/8" | 12.630" | 321 mm | |
| 2 | Tread 2 nose | 25-1/4" | 25.259" | 642 mm | |
| 3 | Tread 3 nose | 37-7/8" | 37.889" | 962 mm | |
| 4 | Tread 4 nose | 50-1/2"+ | 50.519" | 1283 mm | |
| 5 | Tread 5 nose | 63-1/8"+ | 63.149" | 1604 mm | |
| 6 | Tread 6 nose | 75-3/4"+ | 75.778" | 1925 mm | |
| 7 | Tread 7 nose | 88-7/16"− | 88.408" | 2246 mm | |
| 8 | Tread 8 nose | 101-1/16"− | 101.038" | 2566 mm | |
| 9 | Tread 9 nose | 113-11/16"− | 113.668" | 2887 mm | |
| 10 | Tread 10 nose | 126-5/16" | 126.297" | 3208 mm | |
| 11 | Tread 11 nose | 138-15/16" | 138.927" | 3529 mm | |
| 12 | Tread 12 nose | 151-9/16" | 151.557" | 3850 mm | |
| 13 | Top plumb cut | 164-3/16" | 164.187" | 4170 mm |
Then from mark 0 measure 6-5/8" down the bottom riser line and square across for the level heel cut.
Shortest run, steepest legal stair
Gentler climb, longer run
Floor to floor = ceiling + joists + subfloor. With 12-1/2" of floor framing and ceiling, the stairwell opening over Option A starts 10-1/16" from the bottom riser and runs 9' 11-15/16" for 6'-8" of headroom.
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| 0 | Bottom riser line | 0" | 0.000" | 0 mm | 0" |
|---|---|---|---|---|---|
| 1 | Tread 1 nose | 12-5/8" | 12.630" | 321 mm | 1' 5/8" |
| 2 | Tread 2 nose | 25-1/4" | 25.259" | 642 mm | 2' 1-1/4" |
| 3 | Tread 3 nose | 37-7/8" | 37.889" | 962 mm | 3' 1-7/8" |
| 4 | Tread 4 nose | 50-1/2"+ | 50.519" | 1283 mm | 4' 2-1/2" |
| 5 | Tread 5 nose | 63-1/8"+ | 63.149" | 1604 mm | 5' 3-1/8" |
| 6 | Tread 6 nose | 75-3/4"+ | 75.778" | 1925 mm | 6' 3-3/4" |
| 7 | Tread 7 nose | 88-7/16"− | 88.408" | 2246 mm | 7' 4-7/16" |
| 8 | Tread 8 nose | 101-1/16"− | 101.038" | 2566 mm | 8' 5-1/16" |
| 9 | Tread 9 nose | 113-11/16"− | 113.668" | 2887 mm | 9' 5-11/16" |
| 10 | Tread 10 nose | 126-5/16" | 126.297" | 3208 mm | 10' 6-5/16" |
| 11 | Tread 11 nose | 138-15/16" | 138.927" | 3529 mm | 11' 6-15/16" |
| 12 | Tread 12 nose | 151-9/16" | 151.557" | 3850 mm | 12' 7-9/16" |
| 13 | Top plumb cut | 164-3/16" | 164.187" | 4170 mm | 13' 8-3/16" |
Step-off 12-5/8" (12.6297") · bottom cut 6-11/16" under 1" treads · last mark 13' 8-3/16" at the top plumb cut.
| 0 | Bottom riser line | 0" | 0.000" | 0 mm | 0" |
|---|---|---|---|---|---|
| 1 | Tread 1 nose | 13-1/8"+ | 13.147" | 334 mm | 1' 1-1/8" |
| 2 | Tread 2 nose | 26-5/16"− | 26.294" | 668 mm | 2' 2-5/16" |
| 3 | Tread 3 nose | 39-7/16" | 39.441" | 1002 mm | 3' 3-7/16" |
| 4 | Tread 4 nose | 52-9/16"+ | 52.587" | 1336 mm | 4' 4-9/16" |
| 5 | Tread 5 nose | 65-3/4"− | 65.734" | 1670 mm | 5' 5-3/4" |
| 6 | Tread 6 nose | 78-7/8" | 78.881" | 2004 mm | 6' 6-7/8" |
| 7 | Tread 7 nose | 92"+ | 92.028" | 2338 mm | 7' 8" |
| 8 | Tread 8 nose | 105-3/16" | 105.175" | 2671 mm | 8' 9-3/16" |
| 9 | Tread 9 nose | 118-5/16" | 118.322" | 3005 mm | 9' 10-5/16" |
| 10 | Tread 10 nose | 131-7/16"+ | 131.469" | 3339 mm | 10' 11-7/16" |
| 11 | Tread 11 nose | 144-5/8" | 144.615" | 3673 mm | 12' 5/8" |
| 12 | Tread 12 nose | 157-3/4" | 157.762" | 4007 mm | 13' 1-3/4" |
| 13 | Tread 13 nose | 170-15/16"− | 170.909" | 4341 mm | 14' 2-15/16" |
| 14 | Top plumb cut | 184-1/16" | 184.056" | 4675 mm | 15' 4-1/16" |
Step-off 13-1/8"+ (13.1469") · bottom cut 6-3/16" under 1" treads · last mark 15' 4-1/16" at the top plumb cut.
05 / Field guide
This sheet works an 8-ft ceiling (108" floor to floor) two ways. Option A uses the fewest risers the IRC allows, 14 at 7-11/16" on 10" treads. Option B adds one riser and uses 11" treads for a gentler 7-3/16" step. Both come with hook-once tape marks for the stringer edge, below the calculator.
108" ÷ 7.75 = 13.94, rounded up to 14 risers, each 7-11/16"+ (7.7143", 195.9 mm). On 13 treads of 10" the stair lands 130" (10' 10") out from the upper floor edge and climbs at 37.6°; 2R + T scores 25.43".
Each step is 12-5/8" along the stringer edge. Notches cut 6-1/8" deep, leaving 5-1/8" of throat in a 2x12; the cut length is 14' 5/16", so buy 16 ft stock.
One more riser drops each step to 7-3/16" (7.2000"). With 11" treads the run grows to 154" (12' 10"), 24" more than Option A, and the angle eases to 33.2° with 2R + T at 25.40".
The diagonal is 13-1/8"+, the throat 5-1/4", and the stringer cut length 15' 7-7/16" (16 ft).
Take the tread thickness off the bottom riser: 7-11/16" becomes 6-11/16" under 1" 5/4 or composite treads, 6-3/16" under 1-1/2" 2x6 treads and 6-5/8" under 1-1/16" oak treads. Every finished step then measures 7-11/16".
At the top, the last tread notch sits 8-11/16" below the finished floor for 1" treads. Seated on a 2x header, the header top goes 16-7/16" below the finished floor with oak treads.
14 risers means a handrail is required (four or more risers), 34" to 38" above the nosings.
The 130" run is more than the 6'-0" a cut stringer may span under DCA 6: set 1 4x4 support post on 12" footings under the stringers, or build a landing.
The IRC wants 6'-8" measured plumb from the nosing line. With 12-1/2" of floor framing and ceiling, the opening above Option A must start 10-1/16" out from the bottom riser and run 119-15/16" (9' 11-15/16") to the top of the stair.
This sheet assumes a 8 ft (96") ceiling plus 11-1/4" 2x12 joists and a 3/4" subfloor. With 2x10 joists the rise is 106"; use the converter in the calculator for your floor.
Questions
14 risers at 7-11/16" with 13 treads, the fewest the IRC allows. For an easier climb, 15 risers at 7-3/16" with 14 treads.
About 14' 5/16" along the board for Option A, so 16 ft 2x12s; Option B needs 15' 7-7/16" (16 ft).
130" (10' 10") on 10" treads, or 154" (12' 10") on 11" treads with 15 risers. Leave a landing at least 36" deep beyond the last riser.
A 96" ceiling over 2x12 joists and a 3/4" subfloor, or 98" over 2x10s. This is the standard 8 ft ceiling case.
Not under AWC DCA 6, which asks for 2x12s. A 2x10 would keep only 3-1/8" of throat on Option A, under the 5" minimum.
Enter your exact rise in the calculator. 102" takes 14 risers and 114" takes 15; the riser count changes wherever the rise passes a multiple of 7-3/4".
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