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Wallpaper Calculator

Estimates wallpaper rolls by the strip method: the strip length is the wall height plus 10 cm trim, rounded up to a whole pattern repeat; whole strips per roll are counted, door and window areas are deducted and the strips are converted to rolls.

Unit system (optional)Unit system of the length inputs (metric: m / cm / mm; imperial: ft / in). Outputs are reported in both systems. Room perimeter (m or ft) (optional)Total length of the walls to paper (m or ft), e.g. 2 × (length + width). Alternatively give wall_area. Wall height (m or ft)Height to paper (m or ft); 10 cm (4 in) is added per strip for trimming. Gross wall area (m² or ft²) (optional)Gross wall area before openings (m² or ft²); used instead of room_perimeter × wall_height when given. Doors (optional)Number of doors; 1.9 m² (20.5 ft²) is deducted per door. Windows (optional)Number of windows; 1.4 m² (15.1 ft²) is deducted per window. Roll width (m or ft) (optional)Roll width. Default 0.53 m (metric, European roll) or 2.25 ft = 27 in (imperial, American roll). Roll length (m or ft) (optional)Roll length. Default 10.05 m (metric) or 27 ft (imperial). Pattern repeat (cm or in) (optional)Vertical pattern repeat printed on the label (cm or in); 0 for plain or free-match paper. Each strip is rounded up to a whole number of repeats.

When to use

You need to know how many rolls of wallpaper to buy for a room from its perimeter (or wall area), height and the roll dimensions, with or without a pattern repeat.

Do not use when: You are painting (use paint) or boarding (use drywall) the walls, or the paper is a mural sold by the panel.

Formula

strip = wall_height + 0.10 m, rounded up to a multiple of pattern_repeat; strips_per_roll = floor(roll_length / strip); net_area = perimeter × height − 1.9 m² × doors − 1.4 m² × windows; strips_needed = ceil(net_area / (roll_width × wall_height)); rolls = ceil(strips_needed / strips_per_roll).

Rounding each strip up to a whole repeat is the standard allowance for pattern matching; drop (offset) matches can waste up to half a repeat more per strip. Buy all rolls from the same batch number.

Inputs

Parameter	Type	Unit	Required	Description
`unit_system`	enum: metric \| imperial		default metric	Unit system of the length inputs (metric: m / cm / mm; imperial: ft / in). Outputs are reported in both systems.
`room_perimeter`	number	m or ft	no	Total length of the walls to paper (m or ft), e.g. 2 × (length + width). Alternatively give wall_area. Range: > 0, ≤ 10000
`wall_height`	number	m or ft	yes	Height to paper (m or ft); 10 cm (4 in) is added per strip for trimming. Range: > 0, ≤ 100
`wall_area`	number	m² or ft²	no	Gross wall area before openings (m² or ft²); used instead of room_perimeter × wall_height when given. Range: > 0
`doors`	integer		default 1	Number of doors; 1.9 m² (20.5 ft²) is deducted per door. Range: ≥ 0, ≤ 100
`windows`	integer		default 1	Number of windows; 1.4 m² (15.1 ft²) is deducted per window. Range: ≥ 0, ≤ 100
`roll_width`	number	m or ft	no	Roll width. Default 0.53 m (metric, European roll) or 2.25 ft = 27 in (imperial, American roll). Range: > 0, ≤ 10
`roll_length`	number	m or ft	no	Roll length. Default 10.05 m (metric) or 27 ft (imperial). Range: > 0, ≤ 200
`pattern_repeat`	number	cm or in	default 0	Vertical pattern repeat printed on the label (cm or in); 0 for plain or free-match paper. Each strip is rounded up to a whole number of repeats. Range: ≥ 0, ≤ 500

Outputs

Output	Type	Unit	Description
`gross_wall_area_m2`	number	m²	perimeter × height (or wall_area).
`net_wall_area_m2`	number	m²	Gross area minus door and window deductions.
`strip_length_m`	number	m	Height + 0.10 m trim, rounded up to whole pattern repeats.
`strip_length_ft`	number	ft	Strip length in feet.
`strips_per_roll`	integer		floor(roll_length / strip_length).
`strips_needed`	integer		ceil(net_wall_area / (roll_width × wall_height)).
`rolls_needed`	integer		ceil(strips_needed / strips_per_roll).
`roll_size_used`	string		Roll width × length assumed.

Example

16 m perimeter, 2.4 m high, 1 door, 1 window, plain 0.53 × 10.05 m rolls: {"unit_system":"metric","room_perimeter":16,"wall_height":2.4,"doors":1,"windows":1} → {"gross_wall_area_m2":38.4,"net_wall_area_m2":35.1,"strip_length_m":2.5,"strips_per_roll":4,"strips_needed":28,"rolls_needed":7,"roll_size_used":"0.53 m × 10.05 m"}

48 ft perimeter, 8 ft high, 2 doors, 2 windows, 24 in repeat, 27 in × 27 ft rolls: {"unit_system":"imperial","room_perimeter":48,"wall_height":8,"doors":2,"windows":2,"pattern_repeat":24} → {"gross_wall_area_m2":35.67,"net_wall_area_m2":29.07,"strip_length_ft":10,"strips_per_roll":2,"strips_needed":18,"rolls_needed":9}

GET https://tttkmbb.com/api/v1/calculate/wallpaper?unit_system=metric&room_perimeter=16&wall_height=2.4&doors=1&windows=1

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/wallpaper (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/wallpaper · Markdown: https://tttkmbb.com/construction/wallpaper.md · JSON definition: https://tttkmbb.com/construction/wallpaper.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="wallpaper"
OpenAPI operationId: estimate_wallpaper_rolls
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

Wikipedia – Wallpaper (roll sizes, pattern repeat) (reference)

FAQ

Should I buy a spare roll?

Usually yes: one extra roll from the same batch covers mistakes and future repairs, because colours differ slightly between batches.

Why does a pattern repeat need more rolls?

Each strip must start at the same point of the pattern, so it is cut to a whole number of repeats; a 64 cm repeat on a 2.5 m strip means cutting 2.56 m, which reduces the whole strips per 10.05 m roll from 4 to 3.

Related calculators

Paint Calculator — Paint instead of paper for the same walls.
Drywall Calculator — Board the walls before decorating.