Stair Carpet Length Calculator
Measure once, order right. Get the exact carpet length for straight staircases with a landing — including tread, riser, nosing, and waste allowance.
Assumption: Straight run staircase, carpet installed over tread and riser (waterfall method), landing at top or bottom.
Carpet length
—
linear metres
With waste
—
linear metres
Total steps
12
treads + risers
Area (optional)
—
m² if width set
Side-profile staircase
Live visual — updates as you adjust dimensions
Installation assumption: Carpet runs continuously over each tread and down each riser (waterfall method). The nosing is included in the tread measurement. A separate landing length is added if present.
Stair dimensions
Count each horizontal step (tread) — typically 10–16 for a full flight.
Horizontal step depth (including nosing overhang). Standard: 250–280 mm.
Vertical rise between steps. Standard: 170–200 mm.
Rounded edge overhang. Standard: 20–25 mm. Set 0 if included in tread depth.
Horizontal landing at top or bottom. Set 0 if none.
5% plain · 10% patterned · up to 15% for turns. Always round up.
Used to calculate total area (m²). Clear to skip area calculation.
Total carpet needed
12.30 m
including 8% waste
Material breakdown
Every component of the calculation, clearly explained.
Carpet length
—
Tread + riser × stairs + landing
Waste allowance
—
—% of base length
Total material
—
Base + waste, rounded up
Total area
—
Set carpet width to calculate
Step-by-step calculation
How to measure stairs for carpet
Measuring stairs for carpet is not the same as measuring a flat room. You need to account for the horizontal tread, the vertical riser, the nosing overhang, and any landing at the top or bottom of the flight. Getting this wrong means either running short or paying for carpet you will never use.
The standard installation method for stairs is the waterfall method, where a single continuous piece of carpet flows over each tread, down the riser, and over the next tread. This calculator assumes that method. The alternative — separate tread and riser pieces — uses less carpet but creates seams and is less durable.
Tread, riser, and nosing explained
- • Tread depth — the horizontal distance from the front of one step to the front of the next. Typically 250–280 mm in residential stairs.
- • Riser height — the vertical distance between two consecutive treads. Typically 170–200 mm.
- • Nosing — the rounded front edge of the tread that overhangs the riser below. Standard overhang is 20–25 mm. Some carpets are installed with a separate nosing piece for extra durability.
Landing and waste considerations
If your staircase has a landing — a flat platform at the top, bottom, or mid-flight — measure its depth and add it to the total. A typical residential landing is 900–1200 mm deep.
Waste allowance covers pattern matching, trimming, and cutting around newel posts. Use 5% for plain carpet, 10% for patterned carpet, and up to 15% if your stairs turn or have winders. Always round up to the nearest linear metre or foot.
Carpet width and runners
For a full stair carpet, order carpet at least 50–100 mm wider than the stair width so it can be trimmed and tucked. For a stair runner, the runner is typically 20–30 cm narrower than the stair, leaving exposed wood on both sides. This calculator’s optional width input calculates the total area in square metres.
Common mistakes to avoid
- ✕ Forgetting to count the final riser at the top of the stairs.
- ✕ Measuring only the tread and ignoring the riser entirely.
- ✕ Not adding enough waste for patterned carpet with a large repeat.
- ✕ Forgetting the landing when the stairs turn.
Frequently asked questions
Straight answers to common stair carpet questions.
How do you measure stairs for carpet? +
Measure the tread depth, riser height, and landing length. Count the number of stairs. Carpet length = (tread + riser) × number of stairs + landing length. Then add 5–10% waste allowance depending on pattern and turns.
What is a nosing on stairs? +
The nosing is the rounded front edge of the tread that overhangs the riser below. Standard overhang is 20–25 mm. When measuring, either include the nosing in your tread measurement or add it separately — this calculator lets you do both.
How much waste allowance should I add? +
Use 5% for plain carpet, 10% for patterned carpet with a repeat, and 10–15% if your stairs turn or have winders. Always round up to the nearest linear metre or foot.
Does stair carpet need to be wider than the stairs? +
Yes. Order carpet at least 50–100 mm wider than the stair width so it can be trimmed and tucked. For a stair runner, the runner is typically 20–30 cm narrower than the stair, leaving exposed wood on both sides.