A 9 ft ceiling with 2x12 joists (120" floor to floor) needs 16 risers at 7-1/2" and 15 treads: a 150" run on 10" treads, cut from 18 ft 2x12s with 5-1/4" of throat. Gentler: 17 risers at 7-1/16" on 11" treads, a 176" run (2R + T = 25.1").
finished to finished
fewest legal
nosing to nosing
3/4–1-1/4 under 11″
DCA 6 max 18
120" 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 12-1/2" 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 | 12-1/2" | 12.500" | 318 mm | |
| 2 | Tread 2 nose | 25" | 25.000" | 635 mm | |
| 3 | Tread 3 nose | 37-1/2" | 37.500" | 953 mm | |
| 4 | Tread 4 nose | 50" | 50.000" | 1270 mm | |
| 5 | Tread 5 nose | 62-1/2" | 62.500" | 1588 mm | |
| 6 | Tread 6 nose | 75" | 75.000" | 1905 mm | |
| 7 | Tread 7 nose | 87-1/2" | 87.500" | 2223 mm | |
| 8 | Tread 8 nose | 100" | 100.000" | 2540 mm | |
| 9 | Tread 9 nose | 112-1/2" | 112.500" | 2858 mm | |
| 10 | Tread 10 nose | 125" | 125.000" | 3175 mm | |
| 11 | Tread 11 nose | 137-1/2" | 137.500" | 3493 mm | |
| 12 | Tread 12 nose | 150" | 150.000" | 3810 mm | |
| 13 | Tread 13 nose | 162-1/2" | 162.500" | 4128 mm | |
| 14 | Tread 14 nose | 175" | 175.000" | 4445 mm | |
| 15 | Top plumb cut | 187-1/2" | 187.500" | 4763 mm |
Then from mark 0 measure 6-7/16" 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 26-11/16" from the bottom riser and runs 10' 3-5/16" for 6'-8" of headroom.
Sort any column, print a shop sheet, download CSV. Click a row to load it in the calculator.
| 0 | Bottom riser line | 0" | 0.000" | 0 mm | 0" |
|---|---|---|---|---|---|
| 1 | Tread 1 nose | 12-1/2" | 12.500" | 318 mm | 1' 1/2" |
| 2 | Tread 2 nose | 25" | 25.000" | 635 mm | 2' 1" |
| 3 | Tread 3 nose | 37-1/2" | 37.500" | 953 mm | 3' 1-1/2" |
| 4 | Tread 4 nose | 50" | 50.000" | 1270 mm | 4' 2" |
| 5 | Tread 5 nose | 62-1/2" | 62.500" | 1588 mm | 5' 2-1/2" |
| 6 | Tread 6 nose | 75" | 75.000" | 1905 mm | 6' 3" |
| 7 | Tread 7 nose | 87-1/2" | 87.500" | 2223 mm | 7' 3-1/2" |
| 8 | Tread 8 nose | 100" | 100.000" | 2540 mm | 8' 4" |
| 9 | Tread 9 nose | 112-1/2" | 112.500" | 2858 mm | 9' 4-1/2" |
| 10 | Tread 10 nose | 125" | 125.000" | 3175 mm | 10' 5" |
| 11 | Tread 11 nose | 137-1/2" | 137.500" | 3493 mm | 11' 5-1/2" |
| 12 | Tread 12 nose | 150" | 150.000" | 3810 mm | 12' 6" |
| 13 | Tread 13 nose | 162-1/2" | 162.500" | 4128 mm | 13' 6-1/2" |
| 14 | Tread 14 nose | 175" | 175.000" | 4445 mm | 14' 7" |
| 15 | Top plumb cut | 187-1/2" | 187.500" | 4763 mm | 15' 7-1/2" |
Step-off 12-1/2" (12.5000") · bottom cut 6-1/2" under 1" treads · last mark 15' 7-1/2" at the top plumb cut.
| 0 | Bottom riser line | 0" | 0.000" | 0 mm | 0" |
|---|---|---|---|---|---|
| 1 | Tread 1 nose | 13-1/16" | 13.070" | 332 mm | 1' 1-1/16" |
| 2 | Tread 2 nose | 26-1/8" | 26.140" | 664 mm | 2' 2-1/8" |
| 3 | Tread 3 nose | 39-3/16"+ | 39.210" | 996 mm | 3' 3-3/16" |
| 4 | Tread 4 nose | 52-1/4"+ | 52.280" | 1328 mm | 4' 4-1/4" |
| 5 | Tread 5 nose | 65-3/8"− | 65.350" | 1660 mm | 5' 5-3/8" |
| 6 | Tread 6 nose | 78-7/16"− | 78.420" | 1992 mm | 6' 6-7/16" |
| 7 | Tread 7 nose | 91-1/2" | 91.491" | 2324 mm | 7' 7-1/2" |
| 8 | Tread 8 nose | 104-9/16" | 104.561" | 2656 mm | 8' 8-9/16" |
| 9 | Tread 9 nose | 117-5/8" | 117.631" | 2988 mm | 9' 9-5/8" |
| 10 | Tread 10 nose | 130-11/16" | 130.701" | 3320 mm | 10' 10-11/16" |
| 11 | Tread 11 nose | 143-3/4"+ | 143.771" | 3652 mm | 11' 11-3/4" |
| 12 | Tread 12 nose | 156-13/16"+ | 156.841" | 3984 mm | 13' 13/16" |
| 13 | Tread 13 nose | 169-15/16"− | 169.911" | 4316 mm | 14' 1-15/16" |
| 14 | Tread 14 nose | 183"− | 182.981" | 4648 mm | 15' 3" |
| 15 | Tread 15 nose | 196-1/16" | 196.051" | 4980 mm | 16' 4-1/16" |
| 16 | Top plumb cut | 209-1/8" | 209.121" | 5312 mm | 17' 5-1/8" |
Step-off 13-1/16" (13.0701") · bottom cut 6-1/16" under 1" treads · last mark 17' 5-1/8" at the top plumb cut.
05 / Field guide
This sheet works a 9-ft ceiling (120" floor to floor) two ways. Option A uses the fewest risers the IRC allows, 16 at 7-1/2" on 10" treads. Option B adds one riser and uses 11" treads for a gentler 7-1/16" step. Both come with hook-once tape marks for the stringer edge, below the calculator.
120" ÷ 7.75 = 15.48, rounded up to 16 risers, each 7-1/2" (7.5000", 190.5 mm). On 15 treads of 10" the stair lands 150" (12' 6") out from the upper floor edge and climbs at 36.9°; 2R + T scores 25.00".
Each step is 12-1/2" along the stringer edge. Notches cut 6" deep, leaving 5-1/4" of throat in a 2x12; the cut length is 15' 11-3/8", so buy 18 ft stock.
One more riser drops each step to 7-1/16" (7.0588"). With 11" treads the run grows to 176" (14' 8"), 26" more than Option A, and the angle eases to 32.7° with 2R + T at 25.12".
The diagonal is 13-1/16", the throat 5-5/16", and the stringer cut length 17' 8-3/8" (18 ft).
Take the tread thickness off the bottom riser: 7-1/2" becomes 6-1/2" under 1" 5/4 or composite treads, 6" under 1-1/2" 2x6 treads and 6-7/16" under 1-1/16" oak treads. Every finished step then measures 7-1/2".
At the top, the last tread notch sits 8-1/2" below the finished floor for 1" treads. Seated on a 2x header, the header top goes 16-1/4" below the finished floor with oak treads.
16 risers means a handrail is required (four or more risers), 34" to 38" above the nosings.
The 150" run is more than the 6'-0" a cut stringer may span under DCA 6: set 2 4x4 support posts on 12" footings under the stringers, or build a landing.
120" is 24" under the 12'-0" point where DCA 6 requires a landing on deck stairs, and 31" under the 151" IRC limit for one flight.
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 26-11/16" out from the bottom riser and run 123-5/16" (10' 3-5/16") to the top of the stair.
This sheet assumes a 9 ft (108") ceiling plus 11-1/4" 2x12 joists and a 3/4" subfloor. With 2x10 joists the rise is 118"; use the converter in the calculator for your floor.
Questions
16 risers at 7-1/2" with 15 treads, the fewest the IRC allows. For an easier climb, 17 risers at 7-1/16" with 16 treads.
About 15' 11-3/8" along the board for Option A, so 18 ft 2x12s; Option B needs 17' 8-3/8" (18 ft).
150" (12' 6") on 10" treads, or 176" (14' 8") on 11" treads with 17 risers. Leave a landing at least 36" deep beyond the last riser.
A 108" ceiling over 2x12 joists and a 3/4" subfloor, or 110" over 2x10s. This is the standard 9 ft ceiling case.
Not under AWC DCA 6, which asks for 2x12s. A 2x10 would keep only 3-1/4" of throat on Option A, under the 5" minimum.
Enter your exact rise in the calculator. 114" takes 15 risers and 126" takes 17; the riser count changes wherever the rise passes a multiple of 7-3/4".
Raised decks, basements and storeys