THE RIGHT TOOL. A BETTER BUILD. Independent thinking for UK tool buyers
Our approach
MAKE THE NUMBERS USEFUL

Estimate index adjustment calculator

Enter the original cost and the base and target index values from the same chosen series and basis. The target can be a documented observation or your own explicitly chosen scenario; no index or forecast is supplied here.

How the calculation works

Adjusted estimate = base estimate × target index ÷ base index, rounded once to the nearest penny. Change = rounded adjusted estimate − base estimate.

Use the result with care

Use matching index series, scope and reference bases. An index for one type of cost does not establish a change for every item in a project. This does not choose an official index, predict future inflation, adjust dates automatically or guarantee a supplier quotation. A lower target index produces a lower arithmetic estimate. Check whether the base cost already includes any adjustment to avoid counting it twice.

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.