Stair Riser & Tread Chart

The 60-second rule

Risers = ceil(total rise ÷ 7.75). Unit rise = total rise ÷ risers, to the nearest 1/16 in. Total run = (risers − 1) × tread depth — the top step is the upper landing, so it’s not a tread. Stair angle = arctan(unit rise ÷ tread). At the defaults: ceil(105 ÷ 7.75) = 14 risers, 105 ÷ 14 = 7.50 in (7 8/16) unit rise, (14 − 1) × 10 = 130 in run, arctan(7.5 ÷ 10) = 36.9°. Every number above is inside the 2021 IRC limits.

The worked example, line by line

Setup: 105 in floor-to-floor, 10 in tread depth.

Line 1 — riser count. 105 ÷ 7.75 = 13.55 — you can’t build half a riser, so round up to 14 risers. Rounding up is what keeps the unit rise under the 7¾-in legal maximum.

Line 2 — unit rise. 105 ÷ 14 = 7.50 in — 7 8/16 in on a tape measure, comfortably under 7¾ in and identical on every step (the IRC allows at most 3/8 in of variance between the tallest and shortest riser in a flight).

Line 3 — total run. 14 risers mean 13 treads (the top step is the landing): 13 × 10 = 130 in (10 ft 10 in) of horizontal footprint. Plan this number into the floor plan — stairs eat floor space.

Line 4 — stair angle. arctan(7.5 ÷ 10) = 36.9° — a normal, comfortable pitch. Steeper than about 40° starts feeling like a ladder; shallower than 30° wastes space.

Branch — short rise (60 in, e.g. a deck or split level): ceil(60 ÷ 7.75) = 8 risers, 60 ÷ 8 = 7.50 in unit rise, 7 × 10 = 70 in run, 36.9°. Same comfortable numbers — short stairs land on the same rhythm.

Branch — tall rise (144 in = 12 ft, the IRC flight maximum): ceil(144 ÷ 7.75) = 19 risers, 144 ÷ 19 = 7.58 in unit rise, 18 × 10 = 180 in run — but 2021 IRC R311.7.3 caps a single flight at 12 ft of vertical rise between landings, so this staircase requires a landing: build it as two 72-in flights (10 risers each, 7.20 in unit rise, 90 in run per flight) with a landing between them.

The printable reference chart

Common floor-to-floor heights at a 10-in tread depth, all code-checked against the 2021 IRC (max 7¾-in riser). Unit rise is shown decimal and to the nearest 1/16 in for the tape measure. Use your browser’s print button for a clean copy — this chart is print-styled; everything else on the page hides.

Print the chart

Reading the chart: a 96-in rise needs 13 risers at 7.38 in (7 6/16) each with 120 in of run. Risers at 93, 105, and 120 in come out to clean numbers (7¾, 7½, 7½ in) — those are the sweet-spot heights where no 1/16-in fudging is needed.

Output · formula · meaning

Who uses this

• The DIY deck builder: measures a 60-in drop to the patio, gets 8 risers at 7.50 in with 70 in of run, and cuts every stringer the same before lunch.
• The homeowner planning a basement stair: types their 96-in floor-to-floor, reads 13 risers at 7 6/16 in off the chart, and checks the 130-in → 120-in run fits the hallway before calling a framer.
• The home inspector: checks a listing’s stairs against the code numbers — a 9-in tread fails the 10-in minimum outright, and a riser over 7¾ in is a code flag.
• The finish carpenter: uses the 1/16-in unit rise readout (7 11/16 in for a 108-in rise) to lay out the stringer with a framing square — no rounding drift across 14 steps.

Accuracy & limitations

Figures follow the 2021 International Residential Code, R311.7 and R311.7.5 — your local jurisdiction always wins: some cities and states amend the IRC, older homes were built under older codes, and inspectors have final say. This calculator checks riser height and tread depth only; it does not verify headroom (80 in minimum), stair width (36 in minimum), landing sizes, handrail/guarding rules, or the 12-ft flight maximum (it warns about it). Unit rise to 1/16 in is a layout target — real cuts accumulate error, so check the finished risers against the 3/8-in variance rule. Stairs are structural and safety-critical: confirm your layout with a licensed contractor or the local building department before you build.