A 144" floor-to-floor stair needs 19 risers at 7-9/16" and 18 treads: a 180" run on 10" treads, cut from 20 ft 2x12s with 5-3/16" of throat. Gentler: 20 risers at 7-3/16" on 11" treads, a 209" run (2R + T = 25.4").
finished to finished
fewest legal
nosing to nosing
3/4–1-1/4 under 11″
DCA 6 max 18
144" 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 12-9/16" 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 | 12-9/16" | 12.548" | 319 mm | |
| 2 | Tread 2 nose | 25-1/8"− | 25.095" | 637 mm | |
| 3 | Tread 3 nose | 37-5/8"+ | 37.643" | 956 mm | |
| 4 | Tread 4 nose | 50-3/16" | 50.190" | 1275 mm | |
| 5 | Tread 5 nose | 62-3/4" | 62.738" | 1594 mm | |
| 6 | Tread 6 nose | 75-5/16"− | 75.285" | 1912 mm | |
| 7 | Tread 7 nose | 87-13/16"+ | 87.833" | 2231 mm | |
| 8 | Tread 8 nose | 100-3/8" | 100.380" | 2550 mm | |
| 9 | Tread 9 nose | 112-15/16" | 112.928" | 2868 mm | |
| 10 | Tread 10 nose | 125-1/2"− | 125.475" | 3187 mm | |
| 11 | Tread 11 nose | 138"+ | 138.023" | 3506 mm | |
| 12 | Tread 12 nose | 150-9/16" | 150.570" | 3824 mm | |
| 13 | Tread 13 nose | 163-1/8" | 163.118" | 4143 mm | |
| 14 | Tread 14 nose | 175-11/16"− | 175.665" | 4462 mm | |
| 15 | Tread 15 nose | 188-3/16"+ | 188.213" | 4781 mm | |
| 16 | Tread 16 nose | 200-3/4" | 200.760" | 5099 mm | |
| 17 | Tread 17 nose | 213-5/16" | 213.308" | 5418 mm | |
| 18 | Top plumb cut | 225-7/8"− | 225.855" | 5737 mm |
Then from mark 0 measure 6-1/2" 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 57-15/16" from the bottom riser and runs 10' 2-1/16" for 6'-8" of headroom.
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| 0 | Bottom riser line | 0" | 0.000" | 0 mm | 0" |
|---|---|---|---|---|---|
| 1 | Tread 1 nose | 12-9/16" | 12.548" | 319 mm | 1' 9/16" |
| 2 | Tread 2 nose | 25-1/8"− | 25.095" | 637 mm | 2' 1-1/8" |
| 3 | Tread 3 nose | 37-5/8"+ | 37.643" | 956 mm | 3' 1-5/8" |
| 4 | Tread 4 nose | 50-3/16" | 50.190" | 1275 mm | 4' 2-3/16" |
| 5 | Tread 5 nose | 62-3/4" | 62.738" | 1594 mm | 5' 2-3/4" |
| 6 | Tread 6 nose | 75-5/16"− | 75.285" | 1912 mm | 6' 3-5/16" |
| 7 | Tread 7 nose | 87-13/16"+ | 87.833" | 2231 mm | 7' 3-13/16" |
| 8 | Tread 8 nose | 100-3/8" | 100.380" | 2550 mm | 8' 4-3/8" |
| 9 | Tread 9 nose | 112-15/16" | 112.928" | 2868 mm | 9' 4-15/16" |
| 10 | Tread 10 nose | 125-1/2"− | 125.475" | 3187 mm | 10' 5-1/2" |
| 11 | Tread 11 nose | 138"+ | 138.023" | 3506 mm | 11' 6" |
| 12 | Tread 12 nose | 150-9/16" | 150.570" | 3824 mm | 12' 6-9/16" |
| 13 | Tread 13 nose | 163-1/8" | 163.118" | 4143 mm | 13' 7-1/8" |
| 14 | Tread 14 nose | 175-11/16"− | 175.665" | 4462 mm | 14' 7-11/16" |
| 15 | Tread 15 nose | 188-3/16"+ | 188.213" | 4781 mm | 15' 8-3/16" |
| 16 | Tread 16 nose | 200-3/4" | 200.760" | 5099 mm | 16' 8-3/4" |
| 17 | Tread 17 nose | 213-5/16" | 213.308" | 5418 mm | 17' 9-5/16" |
| 18 | Top plumb cut | 225-7/8"− | 225.855" | 5737 mm | 18' 9-7/8" |
Step-off 12-9/16" (12.5475") · bottom cut 6-9/16" under 1" treads · last mark 18' 9-7/8" 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 | Tread 14 nose | 184-1/16" | 184.056" | 4675 mm | 15' 4-1/16" |
| 15 | Tread 15 nose | 197-3/16" | 197.203" | 5009 mm | 16' 5-3/16" |
| 16 | Tread 16 nose | 210-3/8"− | 210.350" | 5343 mm | 17' 6-3/8" |
| 17 | Tread 17 nose | 223-1/2" | 223.497" | 5677 mm | 18' 7-1/2" |
| 18 | Tread 18 nose | 236-5/8"+ | 236.644" | 6011 mm | 19' 8-5/8" |
| 19 | Top plumb cut | 249-13/16"− | 249.790" | 6345 mm | 20' 9-13/16" |
Step-off 13-1/8"+ (13.1469") · bottom cut 6-3/16" under 1" treads · last mark 20' 9-13/16" at the top plumb cut.
05 / Field guide
This sheet works a 144" floor-to-floor rise two ways. Option A uses the fewest risers the IRC allows, 19 at 7-9/16" 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.
144" ÷ 7.75 = 18.58, rounded up to 19 risers, each 7-9/16"+ (7.5789", 192.5 mm). On 18 treads of 10" the stair lands 180" (15' 0") out from the upper floor edge and climbs at 37.2°; 2R + T scores 25.16".
Each step is 12-9/16" along the stringer edge. Notches cut 6-1/16" deep, leaving 5-3/16" of throat in a 2x12; the cut length is 19' 1-13/16", so buy 20 ft stock.
One more riser drops each step to 7-3/16" (7.2000"). With 11" treads the run grows to 209" (17' 5"), 29" 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 21' 1-3/16" (over 20 ft).
Take the tread thickness off the bottom riser: 7-9/16" becomes 6-9/16" under 1" 5/4 or composite treads, 6-1/16" under 1-1/2" 2x6 treads and 6-1/2" under 1-1/16" oak treads. Every finished step then measures 7-9/16".
At the top, the last tread notch sits 8-9/16" below the finished floor for 1" treads. Seated on a 2x header, the header top goes 16-5/16" below the finished floor with oak treads.
19 risers means a handrail is required (four or more risers), 34" to 38" above the nosings.
The 180" 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.
144" is 0" under the 12'-0" point where DCA 6 requires a landing on deck stairs, and 7" 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 57-15/16" out from the bottom riser and run 122-1/16" (10' 2-1/16") to the top of the stair.
Floor to floor is the ceiling height plus the joists and subfloor: 144" is a 132" ceiling over 2x12 joists, or 134" over 2x10s.
Questions
19 risers at 7-9/16" with 18 treads, the fewest the IRC allows. For an easier climb, 20 risers at 7-3/16" with 19 treads.
About 19' 1-13/16" along the board for Option A, so 20 ft 2x12s; Option B needs 21' 1-3/16" (over 20 ft).
180" (15' 0") on 10" treads, or 209" (17' 5") on 11" treads with 20 risers. Leave a landing at least 36" deep beyond the last riser.
A 132" ceiling over 2x12 joists and a 3/4" subfloor, or 134" over 2x10s.
Not under AWC DCA 6, which asks for 2x12s. A 2x10 would keep only 3-3/16" of throat on Option A, under the 5" minimum.
Raised decks, basements and storeys