Free Online Stair Calculator for Carpenter’s & How-To Guide 2025

The Stair Calculator from Daily Life Tools helps beginner carpenters figure out stair rise, run, step height, tread depth, stringer length, stair angle, and the number of steps needed.

It’s a free, easy tool with two options: Automatic Stair Calculator and Manual Stair Calculator. Click the [?] icons to choose the right one for your project.

Are you looking for the Metric (millimeters) version of the Stair Calculator?

Need measurements in millimeters? The Stair Calculator offers a metric version. Just switch to metric mode in the settings to get the numbers you need for your stair-building project.

How to use the stair calculator: Free Online

Check the Stair Calculator on Daily Life Tools. Choose between the Automatic Stair Calculator and the Manual Stair Calculator.

For Automatic Stair Calculator:

• Enter Total Rise [A] (height from bottom to top, e.g., 56.75 inches).
• Set Target Step Height [F] (default is 7 inches).
• Input Tread Thickness [C] (default is 1.5 inches).
• Add Tread Depth [B] (default is 10.5 inches).

For Manual Stair Calculator:

• Enter Total Rise [A] (e.g., 56.75 inches).
• Input Total Run [G] (e.g., 90.5 inches).
• Set Number of Steps (Risers).
• Add Tread Thickness [C].

• Click calculate to see results.
• Check Stair Results for step height, tread depth, and stringer length.
• Use the ??? icons for help on settings.
• Adjust measurements if needed and recalculate.
• Follow the Stair Stringer Diagram to cut and assemble.

Automatic and Manual Stair Calculator

Use our free online Automatic Stair Calculator for easy stair planning—just enter a few details, and it calculates everything for you. Alternatively, the Manual Stair Calculator lets you customize by inputting Total Run [G] and Number of Steps (Risers). Input these for either mode:

Expert Recommendations

Stairs with Risers

Most stairs need solid risers unless the Total Rise is under 30 inches or the Step Height is less than 5.5 inches. Adding risers won’t change the calculator results if you attach them before the treads, as shown in the Stairs with Solid Risers and 2×12 Treads diagram.

Before cutting stringers, check your measurements and plan how to add risers at the top. If you skip a riser at the top (like for a deck), adjust the Tread Depth [B] for the top step to avoid gaps or uneven edges.

Stair Calculator Results and Related Building Codes

The Stair Calculator gives you clear results to build safe, code-approved stairs. This section explains each result and connects it to USA building codes, making it easy for beginners to understand. Always check local rules, as they might differ.

• Stringer: The stringer supports your stairs, usually made from 2×12 wood. The uncut part must be at least 5 inches wide for strength, as shown in the diagrams. For a 36-inch-wide stair, use three stringers (one on each side and one in the middle). The Stringer Length is the total length of the cut 2×12 material.
• Total Rise [A]: This is the height from the first step’s bottom to the top landing. Codes limit it to 151 inches between landings to keep stairs safe.
• Total Run [G]: The horizontal length, figured by multiplying Steps on Stringer [D] by Tread Depth [B]. This ensures the stairs fit your space.
• Risers (Step Height [F]): Each step’s height should not go over 7.75 inches, with less than 3/8 inch difference between steps. Open risers over 30 inches high must block a 4-inch sphere for safety.
• Height of First Step [E]: This is Step Height [F] minus Tread Thickness [C] when cutting the stringer. It keeps the first step level with the others.
• Treads (Tread Depth [B]): Treads need to be at least 10 inches deep, with less than 3/8 inch variation. Use a single 2×12 or two 2x6s for each tread.
• Number of Steps (Risers): This might differ from the Steps on the Stringer [D]. For a Flush mount, risers equal steps. For Standard, add one more riser than steps.
• Stringer Placement [H]: This shows how far below the landing height to attach the stringer for a solid fit.
• Headroom: The space above the steps must be at least 6 feet 8 inches from the tread edge to the ceiling, preventing head bumps.
• Stair/Rail Angle: The angle for cutting rail posts or balusters, ensuring rails fit properly.
• Stringer Length: The minimum 2×12 material length needed for cutting the stringer, based on the diagram’s measurements.
• Stairs and Landings: If Total Rise [A] is over 151 inches, add a landing. Landings must be as wide as the stairs and at least 36 inches deep. See Stairs with Landings for more.

For full details, check the 2024 International Residential Code (IRC), Section 318 – Means of Egress. Confirm with local building officials.

Mobile Stair Calculator vs. Mobile Friendly Stair Calculator

Our Stair Calculator works great on phones, tablets, and computers. Unlike the old version on dailylifetools.com, this one is mobile-friendly and easy to use anywhere.

Try it on your device today!

We welcome your feedback.

Stair Safety Tips

• Ensure the step height is under 7.75 inches per code.
• Keep tread depth at least 10 inches for safe footing.
• Maintain headroom of 6’8″ to avoid head injuries.
• Use solid risers if the rise exceeds 30 inches to prevent falls.
• Check the stair angle for comfortable climbing (around 30-40 degrees).
• Add landings for rises over 151 inches to break the climb.

Choosing the Right Materials

• Use 2×12 or larger for stringers; the uncut portion must be 5 inches.
• Pick 2×12 or two 2x6s for treads to meet depth requirements.
• Select durable wood like oak or pine for longevity.
• Ensure risers are solid if required by code (rise over 30 inches).
• Use pressure-treated wood for outdoor stairs to resist the weather.

Common Stair Building Mistakes

• Not double-checking measurements before cutting stringers.
• Ignoring tread depth consistency (max 3/8 inch variation).
• Skipping risers on stairs over 30 inches, risking safety.
• Misplacing the stringer, causing uneven steps.
• Forgetting to adjust the top step depth if omitting the top riser.

How to Measure Stair Dimensions

• Measure Total Rise [A]: From floor to landing top.
• Measure Total Run [G]: Horizontal space for stairs.
• Count Number of Steps: Divide Total Rise by desired step height.
• Check Tread Depth [B]: Ensure at least 10 inches.
• Measure Stringer Placement [H]: Distance below landing height.

Maintaining Your Stairs

• Inspect for loose treads or risers regularly.
• Tighten bolts or screws on stringers as needed.
• Sand and refinish wood to prevent splinters.
• Clean the stairs to avoid slippery surfaces.
• Replace damaged steps immediately for safety.

DIY Stair Projects for Beginners

• Start with a small indoor staircase (3-4 steps).
• Use the Stair Calculator for accurate measurements.
• Follow the Stair Stringer Diagram to cut stringers.
• Attach solid risers and 2×12 treads as shown in the diagrams.
• Practice on a simple straight staircase before curves.

Cost Estimation for Stair Construction

• Budget for 2×12 stringers: 3 needed for 36-inch-wide stairs.
• Include 2×12 treads or 2x6s: Calculate per step.
• Factor in riser material if required (rise over 30 inches).
• Add cost of nails, screws, and wood finish.
• Account for tools like saws if not already owned.

Frequently Asked Questions (FAQ)

See Also

• Carpentry Calculators: Explore more tools on Daily Life Tools.
• Building Stairs: Get tips on stair construction.
• Stairs and Landings: Learn about adding landings to stairs.

What next?

Try the Stair Calculator now or visit the Daily Life Tools homepage. We’d love your feedback!