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Project budget allowance calculator

Start with an estimate that does not already include the allowance below. Enter any known extra costs separately, then choose a percentage to apply to the combined base. No recommended percentage is supplied.

How the calculation works

Combined base = estimate + known extras. Allowance = combined base × chosen percentage, rounded to the nearest penny. Planning total = combined base + allowance.

Use the result with care

This is a chosen budget allowance, not a probability-based risk model, a quotation or a forecast of actual overspend. Do not count a cost or allowance twice. It cannot establish whether your estimate or chosen allowance is adequate.

Your figures stay in this page

The calculation runs in your browser. These entries are not sent to a calculator service or saved by this tool. Reset returns the form to its starting values.