How much should I budget for a renovation contingency?

A contingency of around 10% to 20% is sensible, because renovations almost always uncover surprises like hidden damage or scope changes. Older homes warrant a larger contingency.

Why do renovations go over budget?

Costs creep in area by area, hidden problems emerge once work starts, and scope grows. Building in a contingency and tracking each category against the budget helps you stay in control.

What costs go into a renovation budget?

Design and consents, demolition, building work, plumbing and electrical, fittings and finishes, and a contingency. This calculator lets you enter each and adds a contingency on top.

Home Renovation Budget Calculator

This New Zealand calculator helps you plan a renovation budget across the major cost areas, with a contingency built in for the surprises that renovations always bring. You enter your figures for each trade and item, and it tracks the running total against your budget and adds a recommended contingency, helping you avoid the classic renovation blowout.

Your total budget

Design and consents

Building work

Plumbing and electrical

Fittings and finishes

Other

Contingency

total project cost including contingency

Costs before contingency$0

Contingency$0

Versus your budget-

A contingency of 10% to 20% is sensible, more for older homes where hidden problems are common. Build it in from the start so a surprise does not derail the project. Estimate only, to support planning.

How it works

The calculator adds your costs across design, building, services, fittings and other, then applies your contingency percentage to that total and adds it on top. The result is a realistic project cost that allows for the surprises renovations bring. It compares this against your budget so you can see whether your plan fits, and trim the scope if it does not before the work starts.

Worked example

Costs of $6,000 design, $35,000 building, $15,000 services, $14,000 fittings and $3,000 other total $73,000. A 15% contingency adds about $10,950, for a project cost of around $83,950, which is over an $80,000 budget, a signal to trim scope or lift the budget before starting.

Related calculators

Mortgage Extra Repayment Calculator: funding from your loan.
Home Equity Calculator: equity to draw on.
Personal Loan Repayment Calculator: financing a reno.
Budget Calculator: household budget.

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