Home improvement
Home Renovation Cost Calculator
Works renovation cost, where the contingency is the most important line.
Result
Renovation carries far more uncertainty than new build because you cannot see behind the walls until demolition. Fifteen to twenty per cent contingency is realistic, not pessimistic.
Get a Free Business AuditHow the calculation works
Each element of work costed, plus permits and professional fees, plus a contingency for what is found. Renovation differs from new construction in that the existing conditions are unknown until they are opened, which makes the contingency a structural part of the budget rather than a cushion.
What moves the number
- Age and condition of the existing structure.
- Whether the work triggers code upgrades.
- Permits and professional fees.
- Living arrangements during the work.
Where this one goes wrong
Work in an older property can trigger requirements to bring parts of it up to current code, which is a scope expansion rather than a surprise cost and depends on what the work touches and the local authority's interpretation. Ask about it before committing. Living in the property during the work is the other underestimated cost, in both money and tolerance, and moving out for a phase is frequently cheaper than the delays of working around occupancy.
Before you quote
- Hold a genuine contingency, not an allocated one.
- Ask what code upgrades the work might trigger.
- Cost the living arrangements during the work.
Where the rules come from
Questions
About this calculator
How much contingency does a renovation need?
Enough that a discovery does not stop the project, which in an older property is more than people allow. It is a structural part of a renovation budget rather than a cushion, because existing conditions are unknown until opened.
Can work trigger code upgrades?
Yes, depending on what the work touches and the local authority's interpretation. Bringing parts of an older property up to current requirements is a scope expansion rather than a surprise, and it is worth asking about before committing.
Should we move out during the work?
It is worth costing, because working around occupancy causes delays and the delays cost money. Moving out for a phase is frequently cheaper overall as well as considerably more tolerable than living in a building site.
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How to use this calculator
- Renovation area (sq ft) (sq ft). Enter your own figure; the page starts at 1,200 sq ft.
- Low-end cost per sq ft ($). Enter your own figure; the page starts at $90.
- High-end cost per sq ft ($). Enter your own figure; the page starts at $240.
- Permits, design and fixed items ($). Enter your own figure; the page starts at $15,000.
- Contingency (%). Enter your own figure; the page starts at 12%.
The result updates as you type, so you can try a figure, see what it does to likely cost, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Renovation area (sq ft) | 1,200 sq ft |
| Low-end cost per sq ft | $90 |
| High-end cost per sq ft | $240 |
| Permits, design and fixed items | $15,000 |
| Contingency | 12% |
What comes out
| Result | Value |
|---|---|
| Likely cost main result | $238,560 |
| Low estimate | $137,760 |
| High estimate | $339,360 |
| All-in cost per sq ft | $198.80 |
Expect roughly $238,560: a range of $137,760 to $339,360 including contingency, or about $198.80 per square foot.
How sensitive the answer is
Holding everything else steady and changing only low-end cost per sq ft, this is what happens to likely cost. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Low-end cost per sq ft ($) | Likely cost |
|---|---|
| $45 | $208,320 |
| $68 | $223,776 |
| $90 example above | $238,560 |
| $135 | $268,800 |
| $180 | $299,040 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Renovation area (sq ft) (sq ft)
- Measured in sq ft, starting at 1,200 sq ft.
- Low-end cost per sq ft ($)
- A money amount, starting at $90.
- High-end cost per sq ft ($)
- A money amount, starting at $240.
- Permits, design and fixed items ($)
- A money amount, starting at $15,000.
- Contingency (%)
- A percentage, between 0 and 50, starting at 12%.
What the results tell you
| Result | What it is |
|---|---|
| Likely cost | The headline result. A money figure. |
| Low estimate | A money figure. |
| High estimate | A money figure. |
| All-in cost per sq ft | A money figure. |
Keep going
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