Stair handrail calculator
How long a rail a straight flight takes, the angle it runs at, the cuts where it meets a post or a level piece, and whether its height and grip pass the 2021 IRC.
Finished floor to finished floor
Bottom riser face to top riser face
Plumb above the nosings
0 for none
Measured level; runs at the slope
One per side
= 3.5"
= 1.75"
Rail length
13 ft 3/16 in
Buy
1 × 14 ft or longer
Rail angle
36.4°
Plumb cut
36.4° off square
Where the length comes from
- Sloped railOver the lowest riser to over the top one: 120" of run, 88 5/8" of rise
- 149 3/16"
- Bottom extension, at the slope
- 0"
- Top extension, level
- 0"
- Wall returns, both ends
- 7"
- One rail
- 156 3/16"
Riser 7 3/8", tread 10". The sloped rail rises one riser less than the 96" floor to floor, because it starts above the first nosing, not at the floor.
Cuts and brackets
- Plumb cut into a newel
- 36.4° off square
- Level cut
- 53.6° off square
- Miter to a level railHalf the rail angle on both sides of the joint
- 18.2° each piece
- Bracket height, square to the slopeThe 36" is plumb; a bracket measured square off the nosing line sits lower
- 28 15/16"
Against the model code
- Rail 34"–38" above the nosings — passesYours is 36", measured plumb from the line through the tread nosings.
- A handrail on at least one side from 4 risers — passes13 risers, so a handrail is required on at least one side.
- Round rail 1 1/4"–2" across — passesYours is 1 3/4" — a hand closes around it.
- Ends returned to the wall — passesReturns of 3 1/2" each, so a sleeve or a bag strap cannot catch an open end.
Checked against the 2021 IRC for residential stairs — defaults, not law. Your jurisdiction may amend them. Ring your building department before you mount anything.
Extensions are a commercial rule
The IRC asks a house's handrail to run from above the top riser to above the bottom one and to return to the wall or die into a post at each end. It does not ask for it to run past either end. Commercial and accessible stairs do: under the IBC and the ADA Standards the rail runs 12" level past the top riser and carries on at the slope for one tread depth past the bottom one. Put those in the extension fields if that is the stair you are building.
Where to buy this
- 1 × handrail, 14 ft or longerHome DepotLowe's
Rail comes in fixed lengths that vary by profile and yard; buy the next length up from the one here, never one that only just reaches.
Plain search links, nothing sponsored. Prices and stock are the shop's, and a local lumberyard will usually beat both on solid stock.
About stair handrails
- How high should a stair handrail be?
- Between 34" and 38" under the 2021 IRC, measured plumb from the sloped line through the tread nosings — not from the tread surface, and not square to the slope. A bracket measured square off the nosing line sits lower than the plumb figure by the cosine of the stair angle, which is why the calculator gives both. That is a different number from a guard's: a floor or landing guard is at least 36", while a guard on the open side of the stair itself may be 34" from the nosings, so one rail in the handrail range can be both. These are defaults, not law — check with your building department.
- How long a handrail do I need for a flight of 13 steps?
- For 96" floor to floor over 13 risers and 120" of run, the sloped rail is 149 3/16" — about 12 ft 5 3/16 in — before any returns or extensions. It is shorter than the 153 11/16" stringer diagonal because the code runs the rail from above the lowest riser to above the top one, which covers one riser less rise than floor to floor. Add a 3 1/2" return at each end and one rail is 156 3/16", so it comes out of a 14 ft length or longer.
- What angle do I cut a handrail at?
- The rail runs at the stair's own angle, which is the riser over the tread: 36.9° for a 7 1/2" riser on a 10" tread. A plumb cut into a newel post is that same 36.9° off square on the miter saw, and a level cut is 53.1°. Where the sloped rail meets a level piece at the top, the rail turns through 36.9°, so each side of the miter is cut at half of it — 18.4°.
- When is a handrail required on stairs?
- The 2021 IRC requires a handrail on at least one side of any flight with 4 or more risers. It has to run continuously from above the top riser to above the bottom one, and each end has to return to the wall or finish in a newel post so nothing can catch on an open end. A house stair does not have to extend past either end; commercial and accessible stairs do, 12" level at the top and one tread's depth at the slope at the bottom, and the calculator has fields for both.
- How thick should a handrail be to be graspable?
- A round rail has to be 1 1/4" to 2" across. A shaped rail passes the same rule if its perimeter is 4" to 6 1/4" and it is no more than 2 1/4" at its widest. Anything bigger around is only allowed with a finger recess down both sides, which is a profile question the calculator cannot see. A rail beside a wall also needs at least 1 1/2" of clear space behind it.
You might also need
- Stair stringersDivide the rise into even risers, lay out the notches, and check the result against the code.
- Baluster and slat spacingEven gaps across any span, checked against the 4-inch guard rule, with tape-measure marks that don't drift.
- Miter angle calculatorThe miter for baseboard, casing or chair rail at any corner angle — flat trim, so there's no bevel to set.