Standard size of tread and riser in stairs

The Standard size of tread and riser in stairs can vary depending on local building codes, but there are generally accepted ranges that are commonly used.

Here are some details on the Standard size of tread and riser in both mm and inches:

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Tread Size

The depth of a tread (the distance from the front edge of the tread to the back edge) is typically between 9 inches (228.6 mm) and 11 inches (279.4 mm).
The width of a tread is typically between 36 inches (914.4 mm) and 48 inches (1219.2 mm) for residential stairs, and up to 72 inches (1828.8 mm) for commercial stairs.

Riser Size

The height of a riser (the distance from the top of one tread to the top of the next) is typically between 7 inches (177.8 mm) and 8 inches (203.2 mm).
The maximum height for a riser is usually 7 3/4 inches (196.85 mm) in the US but can vary by jurisdiction.

In terms of the ratio between riser height and tread depth, there are different accepted standards.

Here are two common ones:

The “7-11” rule: According to the “7-11” rule, the combined distance between the height of a riser and the depth of a tread should fall within the range of 17 inches (431.8 mm) to 18 inches (457.2 mm).

For example, if the riser height is 7 inches, the tread depth should be 10 inches.

If the riser height is 8 inches, the tread depth should be 9 inches.

The “2R + T” rule: This rule states that twice the riser height plus the tread depth should be between 24 inches (609.6 mm) and 25 inches (635 mm).

For example, if the riser height is 7 inches, the tread depth should be between 10 inches and 11 inches.

If the riser height is 8 inches, the tread depth should be between 8 inches and 9 inches.