Choosing a contingency figure
The contingency adds a reserve to the base allowance. It starts at 10%, the lower end of what several published guides suggest. That is a starting point, not an assessment of your project's risk.
What the number does
The reserve is the base allowance multiplied by your percentage, rounded to the nearest penny. It is worked out separately for the low and high ends and added to give the total allowance excluding VAT. Enter 0 to remove it. You can enter up to 50%.
When to consider more
Published guides commonly suggest 10% to 15%, and some up to 20%. You might choose more if the design is still a rough idea, if little is known about the ground or the existing building, or if you couldn't absorb a cost increase. A builder or surveyor can advise on your project.
Avoid counting it twice
If a quote you've entered already includes a contingency, adding another counts it twice.
What a contingency isn't
It covers the unexpected within the priced work. It is not a way to pay for known exclusions such as a kitchen, decoration, professional fees or planning and building control costs. Give those their own figures. The VAT shown on the reserve is illustrative only, because a reserve is a budget amount rather than an invoice.
Trying different figures
Try a few percentages to see how the total changes. Each edit clears the previous result, so note any figures you want to keep.