Plan a safe, code-friendly staircase in seconds. Enter total rise, ideal riser height and tread depth to get step count, exact riser height, total run and stair angle.
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Enter the total rise (floor-to-floor height in inches), your ideal riser height, and your tread depth. The calculator divides the total rise by the ideal riser and rounds UP to a whole number of steps, so no single riser exceeds your target height. It then divides the total rise by that step count to get the exact riser height, which stays identical on every step, a strict code requirement. The number of treads is one less than the number of steps, because the upper floor acts as the final tread, and total run is the tread depth times the tread count. Finally the stair angle comes from arctan(total rise / total run). These are the same formulas professional stair builders use to lay out stringers.
The core move is splitting your total rise into a whole number of equal risers. Dividing the total rise by your ideal riser height almost always gives a decimal, so the count is rounded up to the next whole riser: this keeps every individual riser at or below your target and under code limits. In other words, the total rise vs riser height division tells you how many steps you need, and the actual riser height is then the total rise divided by that whole number, which guarantees every step is exactly the same height. Treads follow as risers minus one, because the upper floor acts as the final tread. Total run is tread depth times the tread count, and the stair angle is the arctangent of total rise over total run.
Measure the total rise first: the vertical distance from the finished lower floor to the finished upper floor, in inches. If flooring is not installed yet, add its thickness, or every step will land wrong. Enter that number, your ideal riser height (7 inches is a comfortable starting point), and your tread depth (10 to 11 inches is standard). The calculator instantly shows the number of steps, the exact riser height you will cut on every stringer, the total horizontal run the stairs will occupy, and the stair angle. Use the total run to confirm the staircase fits your available floor space.
Most US residential work follows the International Residential Code (IRC), which caps riser height at 7.75 inches and requires treads at least 10 inches deep with a nosing, or 11 inches without one. Risers and treads must be consistent through the whole flight, with no more than 3/8 inch variation, since a single uneven step is a classic trip hazard. The stairs need a minimum clear width of 36 inches and at least 6 feet 8 inches of headroom measured from the nosing line. For comfort, aim for risers between 6 and 7.5 inches and apply the 2R+T comfort rule: twice the riser height plus the tread depth should land between 24 and 25 inches. A stair angle between 30 and 37 degrees feels natural to most people; above 40 degrees it starts to feel like a ladder. Always confirm with your local building department, because local amendments can be stricter.
Take a staircase with 96 inches of total rise (an 8 foot floor to floor height), an ideal riser height of 7 inches, and a tread depth of 11 inches. Divide 96 by 7 to get 13.71, which rounds up to 14 risers so no step exceeds the target. The actual riser height is 96 / 14 = 6.86 inches on every step. With 14 risers there are 13 treads, and 13 × 11 = 143 inches of total run (about 11 feet 11 inches). The stair angle is arctan(96 / 143) = 33.9 degrees, right in the comfortable range, and 2R+T = 2(6.86) + 11 = 24.7 inches, which hits the comfort rule. That is the same math the calculator above runs for any rise.
For a 96-inch total rise, divide by your ideal riser height and round up. With a 7-inch target: 96 / 7 = 13.71, so 14 risers. Each riser is then 96 / 14 = 6.86 inches. If your 8-foot ceiling includes floor joists and subfloor, the total rise may be closer to 105-106 inches, which typically needs 15-16 risers.
Most residential builders target 7 to 7.5 inches per riser as the comfortable sweet spot. Building code is a maximum, not a target: the IRC caps risers at 7.75 inches, so anything from 6 to 7.5 inches climbs comfortably while staying well inside the limit.
Under the International Residential Code (IRC), the maximum riser height is 7.75 inches and the minimum tread depth is 10 inches with a nosing, or 11 inches without one. Risers and treads must be uniform through a flight within 3/8 inch, stairs need 36 inches minimum clear width, and headroom must be at least 6 feet 8 inches. Local amendments can differ, so check with your building department.
A standard interior stair tread is 10 to 11 inches deep, which is the horizontal surface your foot lands on. Ten inches is the code minimum when a nosing (front overhang) is used; without a nosing, 11 inches is the minimum. Deeper treads up to about 12 inches feel more comfortable on wide, low-rise stairs.
The 2R+T rule, also called the Blondel formula or the rule of 25, says twice the riser height plus the tread depth should land between 24 and 25 inches for a natural walking stride. For example, a 7-inch riser with an 11-inch tread gives 2(7) + 11 = 25 inches, which is ideal.
Take the arctangent of total rise divided by total run: angle = arctan(total rise / total run). A residential staircase between 30 and 37 degrees feels comfortable. Below 30 degrees it eats up floor space like a ramp; above 40 degrees it feels steep and may break local code.
The stringer is the hypotenuse of the rise-run triangle, so its length is sqrt(total rise² + total run²⁾. For example, a 105-inch rise with a 130-inch run gives sqrt(105² + 130²⁾ = 167.1 inches. Buy lumber longer than this to allow for top and bottom cuts.
Risers are the vertical faces you climb; treads are the flat surfaces you step on. The number of treads is one less than the number of risers, because the upper floor itself acts as the final tread in a standard installation. So 14 risers means 13 treads.
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