Building stairs that feel right isn’t about guesswork. There are numbers that work and numbers that’ll trip you up. Here’s what you need to know.
The Basic Terms
Rise: the vertical height of each step
Run: the horizontal depth of each tread
Tread: the part you step on
Riser: the vertical piece between treads (sometimes open on outdoor stairs)
The Magic Numbers
For residential stairs, rise should be between 7 and 7-3/4 inches. Run should be at least 10 inches.
The classic rule: rise + run should equal about 17-18 inches total. So 7.5″ rise with 10″ run = 17.5″. That feels natural to climb.
Go outside these ranges and stairs feel off. Too steep and you’re climbing. Too shallow and you’re shuffling.
Why Consistency Matters
Every riser has to be the same height. Maximum variation allowed is usually 3/8 inch. More than that and people trip because their feet expect the next step to be where it isn’t.
This is why measuring carefully matters. Calculate your total rise, divide by number of steps, check that it’s within spec.
Building Code
Local codes vary but most follow IRC standards. Maximum riser height 7-3/4″. Minimum tread depth 10″. Minimum headroom 6’8″.
Pull permits if required. Inspectors check stairs carefully because bad stairs cause injuries.
The Math
Measure total rise from finished floor to finished floor. Divide by desired riser height. Round to nearest whole number. That’s your step count.
Recalculate actual riser height using that step count. Adjust if needed.
Common Mistakes
Forgetting to account for flooring thickness. If you’re adding hardwood, measure to finished floor level.
Inconsistent risers because of sloppy cutting. Measure twice, cut once. Actually mark each stringer individually.
Stairs feel harder than they should be? Your rise is probably too steep. Below 7″ feels weird. Above 8″ feels like work.
