The short version: Five measurements decide whether your stairs fit a stair lift, width, step count, total run, turns, landings. Take these before scheduling a dealer visit; saves a wasted appointment if the basics don’t work.

What you’ll need

  • Tape measure (25-foot)
  • Pencil and notepad
  • Phone for photos
  • 5 minutes

The measurements

1. Stair width

Measure clear width at the narrowest point. Include any handrail intrusion.

  • Most stair lifts need 28 inches minimum.
  • Some narrow models (Stannah Sadler) fit 24 inches.
  • Under 24 inches likely doesn’t work.

2. Number of treads

Count steps from bottom to top. Don’t count the floor or the top landing.

A 13-step staircase is common in US homes. Stair lifts handle from about 8 steps to about 20 standard.

3. Total run

Measure along the stair angle from the nose of the top tread to the nose of the bottom tread. A straight string line works.

This determines rail length. Most US straight stair lifts handle 8-20 feet of rail.

4. Turns

The big one. Identify any deviation from straight.

  • Straight: no turns. Simple, cheaper.
  • Quarter turn (90 degrees): one corner. Curved rail required.
  • Half turn (180 degrees): two consecutive 90s, like a U-shape. Curved rail.
  • Spiral: rare. Specialty install.

Any turn means a curved stair lift. Cost roughly triples.

5. Landing space

Top and bottom need clear floor space for the chair to rotate or fold.

  • Bottom: 30+ inches of clear floor in front of the bottom step.
  • Top: 30+ inches before the chair would hit a wall.
  • If either is tight, ask the dealer about hinged-rail or fold-up options.

6. Electrical outlet

Stair lifts run on 120V household current with battery backup. The unit needs an outlet within 6 feet of the top of stairs.

If no outlet exists, add it before install. About $150-$400 with an electrician.

Take photos

Photograph:

  • Full staircase from bottom looking up
  • Full staircase from top looking down
  • Each turn from above
  • Top landing area
  • Bottom landing area
  • Existing handrail attachment

Email the photos to dealers when scheduling. They can pre-screen straight vs curved before the in-home visit.

What kills a stair lift install

  • Stair width under 24 inches (no model fits).
  • No clear landing space at top or bottom.
  • No accessible electrical within reach.
  • Wraparound or split staircases (can sometimes be solved with two separate lifts).

What to do next

Take the measurements this week. Photograph the staircase. Email two dealers (Acorn and Bruno typically) with the data and ask for an initial quote.

For brand picks, see best stair lifts of 2026.

For cost details, see stair lift cost: straight vs curved.

The 30-second summary:
  • 5 measurements: width, step count, total run, turns, landings.
  • Width under 24 inches kills most installs.
  • Any turn = curved stair lift = 3x the cost.
  • Email photos to dealers before scheduling for pre-screening.