A 96" floor-to-floor stair needs 13 risers at 7-3/8" and 12 treads: a 120" run on 10" treads, cut from 14 ft 2x12s with 5-5/16" of throat. Gentler: 14 risers at 6-7/8" on 11" treads, a 143" run (2R + T = 24.7").
finished to finished
fewest legal
nosing to nosing
3/4–1-1/4 under 11″
DCA 6 max 18
96" 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" | 12.431" | 316 mm | |
| 2 | Tread 2 nose | 24-7/8" | 24.862" | 632 mm | |
| 3 | Tread 3 nose | 37-5/16"− | 37.293" | 947 mm | |
| 4 | Tread 4 nose | 49-3/4"− | 49.724" | 1263 mm | |
| 5 | Tread 5 nose | 62-1/8"+ | 62.156" | 1579 mm | |
| 6 | Tread 6 nose | 74-9/16"+ | 74.587" | 1895 mm | |
| 7 | Tread 7 nose | 87"+ | 87.018" | 2210 mm | |
| 8 | Tread 8 nose | 99-7/16" | 99.449" | 2526 mm | |
| 9 | Tread 9 nose | 111-7/8" | 111.880" | 2842 mm | |
| 10 | Tread 10 nose | 124-5/16" | 124.311" | 3158 mm | |
| 11 | Tread 11 nose | 136-3/4" | 136.742" | 3473 mm | |
| 12 | Top plumb cut | 149-3/16" | 149.173" | 3789 mm |
Then from mark 0 measure 6-5/16" 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 0" from the bottom riser and runs 10' 0" 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" | 12.431" | 316 mm | 1' 7/16" |
| 2 | Tread 2 nose | 24-7/8" | 24.862" | 632 mm | 2' 7/8" |
| 3 | Tread 3 nose | 37-5/16"− | 37.293" | 947 mm | 3' 1-5/16" |
| 4 | Tread 4 nose | 49-3/4"− | 49.724" | 1263 mm | 4' 1-3/4" |
| 5 | Tread 5 nose | 62-1/8"+ | 62.156" | 1579 mm | 5' 2-1/8" |
| 6 | Tread 6 nose | 74-9/16"+ | 74.587" | 1895 mm | 6' 2-9/16" |
| 7 | Tread 7 nose | 87"+ | 87.018" | 2210 mm | 7' 3" |
| 8 | Tread 8 nose | 99-7/16" | 99.449" | 2526 mm | 8' 3-7/16" |
| 9 | Tread 9 nose | 111-7/8" | 111.880" | 2842 mm | 9' 3-7/8" |
| 10 | Tread 10 nose | 124-5/16" | 124.311" | 3158 mm | 10' 4-5/16" |
| 11 | Tread 11 nose | 136-3/4" | 136.742" | 3473 mm | 11' 4-3/4" |
| 12 | Top plumb cut | 149-3/16" | 149.173" | 3789 mm | 12' 5-3/16" |
Step-off 12-7/16" (12.4311") · bottom cut 6-3/8" under 1" treads · last mark 12' 5-3/16" at the top plumb cut.
| 0 | Bottom riser line | 0" | 0.000" | 0 mm | 0" |
|---|---|---|---|---|---|
| 1 | Tread 1 nose | 12-15/16"+ | 12.962" | 329 mm | 1' 15/16" |
| 2 | Tread 2 nose | 25-15/16" | 25.925" | 658 mm | 2' 1-15/16" |
| 3 | Tread 3 nose | 38-7/8" | 38.887" | 988 mm | 3' 2-7/8" |
| 4 | Tread 4 nose | 51-7/8"− | 51.849" | 1317 mm | 4' 3-7/8" |
| 5 | Tread 5 nose | 64-13/16" | 64.811" | 1646 mm | 5' 4-13/16" |
| 6 | Tread 6 nose | 77-3/4"+ | 77.774" | 1975 mm | 6' 5-3/4" |
| 7 | Tread 7 nose | 90-3/4" | 90.736" | 2305 mm | 7' 6-3/4" |
| 8 | Tread 8 nose | 103-11/16" | 103.698" | 2634 mm | 8' 7-11/16" |
| 9 | Tread 9 nose | 116-11/16"− | 116.660" | 2963 mm | 9' 8-11/16" |
| 10 | Tread 10 nose | 129-5/8" | 129.623" | 3292 mm | 10' 9-5/8" |
| 11 | Tread 11 nose | 142-9/16"+ | 142.585" | 3622 mm | 11' 10-9/16" |
| 12 | Tread 12 nose | 155-9/16" | 155.547" | 3951 mm | 12' 11-9/16" |
| 13 | Top plumb cut | 168-1/2" | 168.509" | 4280 mm | 14' 1/2" |
Step-off 12-15/16"+ (12.9623") · bottom cut 5-7/8" under 1" treads · last mark 14' 1/2" at the top plumb cut.
05 / Field guide
This sheet works a 96" floor-to-floor rise two ways. Option A uses the fewest risers the IRC allows, 13 at 7-3/8" on 10" treads. Option B adds one riser and uses 11" treads for a gentler 6-7/8" step. Both come with hook-once tape marks for the stringer edge, below the calculator.
96" ÷ 7.75 = 12.39, rounded up to 13 risers, each 7-3/8" (7.3846", 187.6 mm). On 12 treads of 10" the stair lands 120" (10' 0") out from the upper floor edge and climbs at 36.4°; 2R + T scores 24.77".
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 12' 8-15/16", so buy 14 ft stock.
One more riser drops each step to 6-7/8"− (6.8571"). With 11" treads the run grows to 143" (11' 11"), 23" more than Option A, and the angle eases to 31.9° with 2R + T at 24.71".
The diagonal is 12-15/16"+, the throat 5-7/16", and the stringer cut length 14' 3-5/8" (16 ft).
Take the tread thickness off the bottom riser: 7-3/8" becomes 6-3/8" under 1" 5/4 or composite treads, 5-7/8" under 1-1/2" 2x6 treads and 6-5/16" under 1-1/16" oak treads. Every finished step then measures 7-3/8".
At the top, the last tread notch sits 8-3/8" below the finished floor for 1" treads. Seated on a 2x header, the header top goes 16-1/8" below the finished floor with oak treads.
13 risers means a handrail is required (four or more risers), 34" to 38" above the nosings.
The 120" 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 0" out from the bottom riser and run 120" (10' 0") to the top of the stair.
Floor to floor is the ceiling height plus the joists and subfloor: 96" is a 84" ceiling over 2x12 joists, or 86" over 2x10s.
Questions
13 risers at 7-3/8" with 12 treads, the fewest the IRC allows. For an easier climb, 14 risers at 6-7/8" with 13 treads.
About 12' 8-15/16" along the board for Option A, so 14 ft 2x12s; Option B needs 14' 3-5/8" (16 ft).
120" (10' 0") on 10" treads, or 143" (11' 11") on 11" treads with 14 risers. Leave a landing at least 36" deep beyond the last riser.
An 84" ceiling over 2x12 joists and a 3/4" subfloor, or 86" 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. 90" takes 12 risers and 102" takes 14; the riser count changes wherever the rise passes a multiple of 7-3/4".
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