A 102" floor-to-floor stair needs 14 risers at 7-5/16" and 13 treads: a 130" run on 10" treads, cut from 14 ft 2x12s with 5-3/8" of throat. Gentler: 15 risers at 6-13/16" on 11" treads, a 154" run (2R + T = 24.6").
finished to finished
fewest legal
nosing to nosing
3/4–1-1/4 under 11″
DCA 6 max 18
102" 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 12-3/8" 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 | 12-3/8" | 12.373" | 314 mm | |
| 2 | Tread 2 nose | 24-3/4" | 24.745" | 629 mm | |
| 3 | Tread 3 nose | 37-1/8" | 37.118" | 943 mm | |
| 4 | Tread 4 nose | 49-1/2" | 49.490" | 1257 mm | |
| 5 | Tread 5 nose | 61-7/8" | 61.863" | 1571 mm | |
| 6 | Tread 6 nose | 74-1/4" | 74.236" | 1886 mm | |
| 7 | Tread 7 nose | 86-5/8"− | 86.608" | 2200 mm | |
| 8 | Tread 8 nose | 99"− | 98.981" | 2514 mm | |
| 9 | Tread 9 nose | 111-3/8"− | 111.354" | 2828 mm | |
| 10 | Tread 10 nose | 123-3/4"− | 123.726" | 3143 mm | |
| 11 | Tread 11 nose | 136-1/8"− | 136.099" | 3457 mm | |
| 12 | Tread 12 nose | 148-1/2"− | 148.471" | 3771 mm | |
| 13 | Top plumb cut | 160-7/8"− | 160.844" | 4085 mm |
Then from mark 0 measure 6-1/4" 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 3-1/16" from the bottom riser and runs 10' 6-15/16" for 6'-8" of headroom.
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| 0 | Bottom riser line | 0" | 0.000" | 0 mm | 0" |
|---|---|---|---|---|---|
| 1 | Tread 1 nose | 12-3/8" | 12.373" | 314 mm | 1' 3/8" |
| 2 | Tread 2 nose | 24-3/4" | 24.745" | 629 mm | 2' 3/4" |
| 3 | Tread 3 nose | 37-1/8" | 37.118" | 943 mm | 3' 1-1/8" |
| 4 | Tread 4 nose | 49-1/2" | 49.490" | 1257 mm | 4' 1-1/2" |
| 5 | Tread 5 nose | 61-7/8" | 61.863" | 1571 mm | 5' 1-7/8" |
| 6 | Tread 6 nose | 74-1/4" | 74.236" | 1886 mm | 6' 2-1/4" |
| 7 | Tread 7 nose | 86-5/8"− | 86.608" | 2200 mm | 7' 2-5/8" |
| 8 | Tread 8 nose | 99"− | 98.981" | 2514 mm | 8' 3" |
| 9 | Tread 9 nose | 111-3/8"− | 111.354" | 2828 mm | 9' 3-3/8" |
| 10 | Tread 10 nose | 123-3/4"− | 123.726" | 3143 mm | 10' 3-3/4" |
| 11 | Tread 11 nose | 136-1/8"− | 136.099" | 3457 mm | 11' 4-1/8" |
| 12 | Tread 12 nose | 148-1/2"− | 148.471" | 3771 mm | 12' 4-1/2" |
| 13 | Top plumb cut | 160-7/8"− | 160.844" | 4085 mm | 13' 4-7/8" |
Step-off 12-3/8" (12.3726") · bottom cut 6-5/16" under 1" treads · last mark 13' 4-7/8" at the top plumb cut.
| 0 | Bottom riser line | 0" | 0.000" | 0 mm | 0" |
|---|---|---|---|---|---|
| 1 | Tread 1 nose | 12-15/16" | 12.932" | 328 mm | 1' 15/16" |
| 2 | Tread 2 nose | 25-7/8" | 25.864" | 657 mm | 2' 1-7/8" |
| 3 | Tread 3 nose | 38-13/16"− | 38.796" | 985 mm | 3' 2-13/16" |
| 4 | Tread 4 nose | 51-3/4"− | 51.729" | 1314 mm | 4' 3-3/4" |
| 5 | Tread 5 nose | 64-11/16"− | 64.661" | 1642 mm | 5' 4-11/16" |
| 6 | Tread 6 nose | 77-9/16"+ | 77.593" | 1971 mm | 6' 5-9/16" |
| 7 | Tread 7 nose | 90-1/2"+ | 90.525" | 2299 mm | 7' 6-1/2" |
| 8 | Tread 8 nose | 103-7/16"+ | 103.457" | 2628 mm | 8' 7-7/16" |
| 9 | Tread 9 nose | 116-3/8" | 116.389" | 2956 mm | 9' 8-3/8" |
| 10 | Tread 10 nose | 129-5/16" | 129.321" | 3285 mm | 10' 9-5/16" |
| 11 | Tread 11 nose | 142-1/4" | 142.253" | 3613 mm | 11' 10-1/4" |
| 12 | Tread 12 nose | 155-3/16" | 155.186" | 3942 mm | 12' 11-3/16" |
| 13 | Tread 13 nose | 168-1/8" | 168.118" | 4270 mm | 14' 1/8" |
| 14 | Top plumb cut | 181-1/16" | 181.050" | 4599 mm | 15' 1-1/16" |
Step-off 12-15/16" (12.9321") · bottom cut 5-13/16" under 1" treads · last mark 15' 1-1/16" at the top plumb cut.
05 / Field guide
This sheet works a 102" floor-to-floor rise two ways. Option A uses the fewest risers the IRC allows, 14 at 7-5/16" on 10" treads. Option B adds one riser and uses 11" treads for a gentler 6-13/16" step. Both come with hook-once tape marks for the stringer edge, below the calculator.
102" ÷ 7.75 = 13.16, rounded up to 14 risers, each 7-5/16"− (7.2857", 185.1 mm). On 13 treads of 10" the stair lands 130" (10' 10") out from the upper floor edge and climbs at 36.1°; 2R + T scores 24.57".
Each step is 12-3/8" along the stringer edge. Notches cut 5-7/8" deep, leaving 5-3/8" of throat in a 2x12; the cut length is 13' 8-9/16", so buy 14 ft stock.
One more riser drops each step to 6-13/16" (6.8000"). With 11" treads the run grows to 154" (12' 10"), 24" more than Option A, and the angle eases to 31.7° with 2R + T at 24.60".
The diagonal is 12-15/16", the throat 5-7/16", and the stringer cut length 15' 4-1/8" (16 ft).
Take the tread thickness off the bottom riser: 7-5/16" becomes 6-5/16" under 1" 5/4 or composite treads, 5-13/16" under 1-1/2" 2x6 treads and 6-1/4" under 1-1/16" oak treads. Every finished step then measures 7-5/16".
At the top, the last tread notch sits 8-5/16" below the finished floor for 1" treads. Seated on a 2x header, the header top goes 16-1/16" 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 3-1/16" out from the bottom riser and run 126-15/16" (10' 6-15/16") to the top of the stair.
Floor to floor is the ceiling height plus the joists and subfloor: 102" is a 90" ceiling over 2x12 joists, or 92" over 2x10s.
Questions
14 risers at 7-5/16" with 13 treads, the fewest the IRC allows. For an easier climb, 15 risers at 6-13/16" with 14 treads.
About 13' 8-9/16" along the board for Option A, so 14 ft 2x12s; Option B needs 15' 4-1/8" (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 90" ceiling over 2x12 joists and a 3/4" subfloor, or 92" over 2x10s.
Not under AWC DCA 6, which asks for 2x12s. A 2x10 would keep only 3-3/8" of throat on Option A, under the 5" minimum.
Enter your exact rise in the calculator. 96" takes 13 risers and 108" takes 14; the riser count changes wherever the rise passes a multiple of 7-3/4".
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