Stairs Calculator
A stairs calculator helps you plan every dimension of a staircase before you cut a single board. Enter your total rise, choose your preferred step height, and the tool instantly shows you the number of steps, exact rise per step, total run, stringer length, and material estimates. Every number updates in real time as you adjust.
People use this tool in many situations. Homeowners building a deck use it to plan outdoor stairs that meet safety codes. Contractors use it to verify stair dimensions before framing. Carpenters use it to calculate stringer length and cut angles. Architects use it to check that their designs meet building code requirements. DIY builders use it to plan interior stair renovations. Inspectors use it to verify that existing stairs meet code. Anyone building or remodeling stairs can use it to get accurate numbers in seconds.
The tool works with any measurement system. Enter your total rise in inches or centimeters and the tool handles the rest. It offers building code presets for common standards like the International Residential Code which limits residential stair rise to 7.75 inches and requires a minimum tread depth of 10 inches. You can also enter your own preferred rise and tread to match your specific project. Additional fields cover stair width, nosing, and material type.
Every result includes step by step dimensions, total run, stringer length, and cut angle. It also includes a materials estimate so you know how much lumber you need. Every result comes with a copy button. The tool runs in your browser, needs no signup, and works on desktop and mobile.
Enter your total rise and instantly see your complete stair plan.
Frequently Asked Questions About Stairs Calculator
Is this stairs calculator free to use?
Yes. The tool is completely free with no signup, no limits, and no hidden charges.
How does the stairs calculator work?
Enter your total rise (the height from one floor to the next). The tool calculates the number of steps, the exact rise per step, total run, stringer length, and cut angles. Every result updates live as you type.
What is the maximum stair rise allowed by building code?
The International Residential Code allows a maximum rise of 7.75 inches (196 mm) per step for residential stairs. Commercial stairs are often limited to 7 inches. Always verify with your local building department.
What is the minimum tread depth for stairs?
The IRC requires a minimum tread depth of 10 inches (254 mm) for residential stairs. Some regions require 11 inches. Deeper treads are more comfortable and safer.
How do I calculate the number of steps?
Divide the total rise by your preferred rise per step. For example, a 108 inch total rise divided by 7.5 inches per step equals 14.4 steps. Round up to the nearest whole number, which gives 15 steps in this case.
What is the 2R + T rule?
The 2R + T rule states that twice the rise plus the tread depth should equal between 24 and 25 inches for comfortable stairs. For example, a 7 inch rise with an 11 inch tread gives 2×7+11=25, which is ideal.
How long should a stringer be?
The stringer length equals the square root of (total rise squared + total run squared). The tool calculates this automatically.
Can I use this for deck stairs or interior stairs?
Yes. The calculator works for both exterior and interior stairs. Adjust the rise and tread based on your local code and material.