A stair riser and tread calculator determines the optimal number of steps, riser height, and tread depth for any floor-to-floor rise. Building codes (IBC/IRC) require risers no taller than 7-3/4" and treads no shallower than 10". Enter your measurements below for code-compliant stair dimensions.
Stair Dimensions
Stair Design Results
Enter your floor-to-floor rise to calculate.
IBC / IRC Code Requirements
How to Use the Stair Riser and Tread Calculator
Calculating proper stair dimensions is critical for both safety and code compliance. This stair riser and tread calculator uses IBC and IRC standards to ensure your stairs meet building requirements.
Step 1: Measure Total Rise
Measure the vertical distance from the finished floor at the bottom of the stairs to the finished floor at the top. This is your total rise. Include any flooring material thickness (carpet adds ~3/8", hardwood adds ~3/4") in your measurement. A typical 9-foot ceiling floor-to-floor equals about 108 inches including floor framing.
Step 2: Enter Preferred Dimensions
Enter your preferred riser height (how tall each step is) and tread depth (how deep each step platform is). Standard residential stairs use 7-inch risers with 11-inch treads. The calculator will adjust these to evenly divide your total rise while staying within code limits.
Step 3: Review the Code Check
The calculator checks your results against IBC requirements: maximum 7-3/4" riser height and minimum 10" tread depth. A green "Code Compliant" indicator means your stairs meet standard requirements. Yellow warnings flag potential concerns worth discussing with your inspector.
Understanding Total Run
Total run is the horizontal floor space your staircase requires. It equals the number of treads multiplied by the tread depth. For a 15-riser stair with 11" treads, total run = 14 treads × 11" = 154 inches (12.8 feet). Make sure you have this space available before finalizing your design.
Comfort Formula
The traditional comfort rule is: (2 × riser height) + tread depth = 24-25 inches. A 7" riser with an 11" tread gives 7×2+11 = 25 — ideal. Stairs outside this range feel awkward: too steep if the sum exceeds 25, too gradual if it falls below 24.
FAQ
Is this stair calculator free to use?
Yes, the stair riser and tread calculator is completely free with no limits or signup required. All calculations run locally in your browser and no data is sent to a server.
What is the maximum riser height per building code?
The International Building Code (IBC) sets a maximum riser height of 7-3/4 inches (7.75") for residential stairs. The IRC (International Residential Code) matches this limit. Commercial stairs may have a lower maximum. Riser heights must also be consistent — no single riser can vary more than 3/8" from the others.
What is the minimum tread depth for stairs?
Per the IBC and IRC, the minimum tread depth is 10 inches, measured horizontally from nosing to nosing. A comfortable tread is typically 11-12 inches. Deeper treads are especially important for open-tread stairs without risers.
How do I calculate the number of stairs I need?
Divide the total floor-to-floor rise by your desired riser height. For example, 9 feet (108 inches) ÷ 7 inches = 15.4, which rounds to 15 risers. Then divide the actual rise by the number of risers to get the exact riser height: 108 ÷ 15 = 7.2 inches per riser. Note: you need one fewer tread than risers in most stair configurations.
What is the comfortable riser-to-tread ratio?
The traditional comfort formula is: 2 × riser height + tread depth = 24-25 inches. For example, a 7" riser with an 11" tread = 25, which is comfortable. A 7.5" riser with a 10" tread = 25 also works. Going outside this range creates stairs that feel steep or awkward to climb.
What is stair total run vs total rise?
Total rise is the vertical height from floor to floor — the height your stairs must climb. Total run is the horizontal distance the stairs occupy — how much floor space they take. Total run = (number of treads) × (tread depth). Always verify you have sufficient floor space for the total run before finalizing your stair design.