A 126" floor-to-floor stair needs 17 risers at 7-7/16" and 16 treads: a 160" run on 10" treads, cut from 18 ft 2x12s with 5-5/16" of throat. Gentler: 18 risers at 7" on 11" treads, a 187" run (2R + T = 25.0").
finished to finished
fewest legal
nosing to nosing
3/4–1-1/4 under 11″
DCA 6 max 18
126" 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 12-7/16" 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 | 12-7/16" | 12.447" | 316 mm | |
| 2 | Tread 2 nose | 24-7/8"+ | 24.895" | 632 mm | |
| 3 | Tread 3 nose | 37-5/16"+ | 37.342" | 948 mm | |
| 4 | Tread 4 nose | 49-13/16"− | 49.789" | 1265 mm | |
| 5 | Tread 5 nose | 62-1/4" | 62.236" | 1581 mm | |
| 6 | Tread 6 nose | 74-11/16" | 74.684" | 1897 mm | |
| 7 | Tread 7 nose | 87-1/8" | 87.131" | 2213 mm | |
| 8 | Tread 8 nose | 99-9/16" | 99.578" | 2529 mm | |
| 9 | Tread 9 nose | 112"+ | 112.025" | 2845 mm | |
| 10 | Tread 10 nose | 124-1/2"− | 124.473" | 3162 mm | |
| 11 | Tread 11 nose | 136-15/16"− | 136.920" | 3478 mm | |
| 12 | Tread 12 nose | 149-3/8" | 149.367" | 3794 mm | |
| 13 | Tread 13 nose | 161-13/16" | 161.814" | 4110 mm | |
| 14 | Tread 14 nose | 174-1/4" | 174.262" | 4426 mm | |
| 15 | Tread 15 nose | 186-11/16"+ | 186.709" | 4742 mm | |
| 16 | Top plumb cut | 199-1/8"+ | 199.156" | 5059 mm |
Then from mark 0 measure 6-3/8" 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 35-3/16" from the bottom riser and runs 10' 4-13/16" for 6'-8" of headroom.
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| 0 | Bottom riser line | 0" | 0.000" | 0 mm | 0" |
|---|---|---|---|---|---|
| 1 | Tread 1 nose | 12-7/16" | 12.447" | 316 mm | 1' 7/16" |
| 2 | Tread 2 nose | 24-7/8"+ | 24.895" | 632 mm | 2' 7/8" |
| 3 | Tread 3 nose | 37-5/16"+ | 37.342" | 948 mm | 3' 1-5/16" |
| 4 | Tread 4 nose | 49-13/16"− | 49.789" | 1265 mm | 4' 1-13/16" |
| 5 | Tread 5 nose | 62-1/4" | 62.236" | 1581 mm | 5' 2-1/4" |
| 6 | Tread 6 nose | 74-11/16" | 74.684" | 1897 mm | 6' 2-11/16" |
| 7 | Tread 7 nose | 87-1/8" | 87.131" | 2213 mm | 7' 3-1/8" |
| 8 | Tread 8 nose | 99-9/16" | 99.578" | 2529 mm | 8' 3-9/16" |
| 9 | Tread 9 nose | 112"+ | 112.025" | 2845 mm | 9' 4" |
| 10 | Tread 10 nose | 124-1/2"− | 124.473" | 3162 mm | 10' 4-1/2" |
| 11 | Tread 11 nose | 136-15/16"− | 136.920" | 3478 mm | 11' 4-15/16" |
| 12 | Tread 12 nose | 149-3/8" | 149.367" | 3794 mm | 12' 5-3/8" |
| 13 | Tread 13 nose | 161-13/16" | 161.814" | 4110 mm | 13' 5-13/16" |
| 14 | Tread 14 nose | 174-1/4" | 174.262" | 4426 mm | 14' 6-1/4" |
| 15 | Tread 15 nose | 186-11/16"+ | 186.709" | 4742 mm | 15' 6-11/16" |
| 16 | Top plumb cut | 199-1/8"+ | 199.156" | 5059 mm | 16' 7-1/8" |
Step-off 12-7/16" (12.4473") · bottom cut 6-7/16" under 1" treads · last mark 16' 7-1/8" at the top plumb cut.
| 0 | Bottom riser line | 0" | 0.000" | 0 mm | 0" |
|---|---|---|---|---|---|
| 1 | Tread 1 nose | 13-1/16"− | 13.038" | 331 mm | 1' 1-1/16" |
| 2 | Tread 2 nose | 26-1/16" | 26.077" | 662 mm | 2' 2-1/16" |
| 3 | Tread 3 nose | 39-1/8" | 39.115" | 994 mm | 3' 3-1/8" |
| 4 | Tread 4 nose | 52-1/8"+ | 52.154" | 1325 mm | 4' 4-1/8" |
| 5 | Tread 5 nose | 65-3/16" | 65.192" | 1656 mm | 5' 5-3/16" |
| 6 | Tread 6 nose | 78-1/4"− | 78.230" | 1987 mm | 6' 6-1/4" |
| 7 | Tread 7 nose | 91-1/4"+ | 91.269" | 2318 mm | 7' 7-1/4" |
| 8 | Tread 8 nose | 104-5/16" | 104.307" | 2649 mm | 8' 8-5/16" |
| 9 | Tread 9 nose | 117-3/8"− | 117.346" | 2981 mm | 9' 9-3/8" |
| 10 | Tread 10 nose | 130-3/8" | 130.384" | 3312 mm | 10' 10-3/8" |
| 11 | Tread 11 nose | 143-7/16" | 143.422" | 3643 mm | 11' 11-7/16" |
| 12 | Tread 12 nose | 156-7/16"+ | 156.461" | 3974 mm | 13' 7/16" |
| 13 | Tread 13 nose | 169-1/2" | 169.499" | 4305 mm | 14' 1-1/2" |
| 14 | Tread 14 nose | 182-9/16"− | 182.538" | 4636 mm | 15' 2-9/16" |
| 15 | Tread 15 nose | 195-9/16" | 195.576" | 4968 mm | 16' 3-9/16" |
| 16 | Tread 16 nose | 208-5/8" | 208.614" | 5299 mm | 17' 4-5/8" |
| 17 | Top plumb cut | 221-5/8"+ | 221.653" | 5630 mm | 18' 5-5/8" |
Step-off 13-1/16"− (13.0384") · bottom cut 6" under 1" treads · last mark 18' 5-5/8" at the top plumb cut.
05 / Field guide
This sheet works a 126" floor-to-floor rise two ways. Option A uses the fewest risers the IRC allows, 17 at 7-7/16" on 10" treads. Option B adds one riser and uses 11" treads for a gentler 7" step. Both come with hook-once tape marks for the stringer edge, below the calculator.
126" ÷ 7.75 = 16.26, rounded up to 17 risers, each 7-7/16"− (7.4118", 188.3 mm). On 16 treads of 10" the stair lands 160" (13' 4") out from the upper floor edge and climbs at 36.5°; 2R + T scores 24.82".
Each step is 12-7/16" along the stringer edge. Notches cut 5-15/16" deep, leaving 5-5/16" of throat in a 2x12; the cut length is 16' 11", so buy 18 ft stock.
One more riser drops each step to 7" (7.0000"). With 11" treads the run grows to 187" (15' 7"), 27" more than Option A, and the angle eases to 32.5° with 2R + T at 25.00".
The diagonal is 13-1/16"−, the throat 5-3/8", and the stringer cut length 18' 8-7/8" (20 ft).
Take the tread thickness off the bottom riser: 7-7/16" becomes 6-7/16" under 1" 5/4 or composite treads, 5-15/16" under 1-1/2" 2x6 treads and 6-3/8" under 1-1/16" oak treads. Every finished step then measures 7-7/16".
At the top, the last tread notch sits 8-7/16" below the finished floor for 1" treads. Seated on a 2x header, the header top goes 16-3/16" below the finished floor with oak treads.
17 risers means a handrail is required (four or more risers), 34" to 38" above the nosings.
The 160" 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.
126" is 18" under the 12'-0" point where DCA 6 requires a landing on deck stairs, and 25" 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 35-3/16" out from the bottom riser and run 124-13/16" (10' 4-13/16") to the top of the stair.
Floor to floor is the ceiling height plus the joists and subfloor: 126" is a 114" ceiling over 2x12 joists, or 116" over 2x10s.
Questions
17 risers at 7-7/16" with 16 treads, the fewest the IRC allows. For an easier climb, 18 risers at 7" with 17 treads.
About 16' 11" along the board for Option A, so 18 ft 2x12s; Option B needs 18' 8-7/8" (20 ft).
160" (13' 4") on 10" treads, or 187" (15' 7") on 11" treads with 18 risers. Leave a landing at least 36" deep beyond the last riser.
A 114" ceiling over 2x12 joists and a 3/4" subfloor, or 116" over 2x10s.
Not under AWC DCA 6, which asks for 2x12s. A 2x10 would keep only 3-5/16" of throat on Option A, under the 5" minimum.
Enter your exact rise in the calculator. 120" takes 16 risers and 132" takes 18; the riser count changes wherever the rise passes a multiple of 7-3/4".
Raised decks, basements and storeys