Determine Number of Treads

What happens in this clip

A critical rule in stair layout is that the number of treads is always one less than the number of risers. This is because the deck itself serves as the final top step, eliminating the need for an additional tread at the very top. So, if you have 8 risers, you will need 7 treads.

Goal: Apply the 'number of risers minus one' rule to find the correct number of treads needed for your stair stringers.

About the full video

This video provides step-by-step instructions for accurately laying out deck stair stringers by calculating the total rise, determining the number of risers and treads, and then calculating the total run to find the precise landing point for the stairs. This method helps avoid common mistakes in stair construction.

Step 5 of 7: Calculate the Number of Treads

The number of treads is always one less than the number of risers. This is because the upper floor serves as the final 'tread'. Using the number of risers from Step 3, subtract one to find the number of treads. If you have 14 risers, you will need 13 treads.

Open this step in the guide

Every video in How to Calculate How Many Stairs You Need

1. Step 1: Measure the Total Rise

   • 0:15–0:29 Measure Total Rise
   • 0:01–0:28 Measure Total Vertical Rise
   • 0:17–0:31 Measure Total Rise

2. Step 2: Determine the Ideal Riser Height

   • 1:03–1:44 Calculate Riser Height (Option 1)
   • 1:44–2:33 Calculate Riser Height (Option 2) and Verify Code Compliance
   • 4:32–5:10 Calculate Individual Riser Height

3. Step 3: Calculate the Number of Risers

   • 0:32–0:54 Calculate Number of Risers
   • 8:59–9:54 Calculate Number of Risers and Treads
   • 7:42–8:55 Calculate Number of Risers

4. Step 4: Recalculate Actual Riser Height

   • 1:03–1:44 Calculate Riser Height (Option 1)
   • 4:32–5:10 Calculate Individual Riser Height
   • 1:44–2:33 Calculate Riser Height (Option 2) and Verify Code Compliance

5. Step 5: Calculate the Number of Treads

   • 3:54–5:04 Calculate the Number of Treads and Understand the Logic
   • 0:54–1:13 Determine Number of Treads (this video)
   • 8:59–9:54 Calculate Number of Risers and Treads

6. Step 6: Determine the Total Run

   • 1:13–1:29 Calculate Total Run
   • 1:31–2:57 Calculate Unit Run and Total Run
   • 6:51–8:30 Calculate Total Run

7. Step 7: Calculate Tread Depth

   • 2:05–2:24 Calculate Individual Riser Height & Tread Depth
   • 9:54–10:28 Determine Tread Run and Total Run
   • 8:50–10:30 Calculate Risers, Treads, and Total Run