Calculating your rolls needed is straightforward once you know the Wallpaper formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Wallpaper Calculator.
What is Wallpaper?
The Wallpaper calculation tells you your rolls needed from a few simple inputs. The figure you are solving for here is the rolls needed.
The Wallpaper formula
This calculation combines several inputs through a multi-step method rather than a single one-line formula. Enter the values below and the calculator resolves each step in order. The inputs it needs are:
- Total wall area — a value measured in sq ft. Example: 400 sq ft.
- Coverage per roll — a value measured in sq ft. Example: 56 sq ft.
- Wastage allowance — a percentage, such as an annual rate. Example: 15%.
How to calculate it step by step
- Write down the total wall area (for example, 400 sq ft).
- Write down the coverage per roll (for example, 56 sq ft).
- Write down the wastage allowance (for example, 15%).
- Apply the formula above to get your rolls needed.
- Double-check the result with the Wallpaper Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Total wall area | 400 sq ft |
| Coverage per roll | 56 sq ft |
| Wastage allowance | 15% |
| Rolls needed | 9 |
With total wall area of 400 sq ft, coverage per roll of 56 sq ft and wastage allowance of 15%, the rolls needed works out to 9.
Example 2
With total wall area of 800 sq ft, coverage per roll of 56 sq ft and wastage allowance of 15%, the rolls needed works out to 17.
| Result | Value |
|---|---|
| Rolls needed | 17 |
Example 3
With total wall area of 200 sq ft, coverage per roll of 56 sq ft and wastage allowance of 15%, the rolls needed works out to 5.
| Result | Value |
|---|---|
| Rolls needed | 5 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Wallpaper Calculator does it instantly, for free, with the formula and a worked example built in.
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