Calculate the Number of Treads and Understand the Logic

What happens in this clip

The number of treads is calculated using the formula: Number of Treads = Number of Risers - 1. This rule is explained by a small illustrative diagram, demonstrating that the final 'tread' of the staircase is typically the floor slab of the upper level, and therefore not considered a separate, individual tread that needs to be constructed as part of the staircase run. Therefore, if there are 22 risers, the number of treads will be 22 - 1 = 21 treads.

Goal: Determine the quantity of treads and understand their relation to risers

What's used

Tools

• Marker
• Whiteboard

About the full video

This project provides a step-by-step guide on how to calculate the basic dimensions for designing a staircase. It covers assuming appropriate riser and tread dimensions, determining the number of steps and treads, understanding staircase width guidelines, and calculating the total horizontal distance (run). The video emphasizes practical units (feet) for construction site applications.

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 (this video)
   • 0:54–1:13 Determine Number of Treads
   • 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