Budgeting a renovation
The renovation budget spreadsheet, and where it breaks
A template with working formulas, the row structure that survives a real job, and an honest account of the point at which a spreadsheet stops being the right tool. You will probably use one anyway — this is how to use it well.
Download the template
Opens in Excel, Numbers or Google Sheets. Subtotals, contingency and variance are real formulas, not typed-in numbers. No sign-up.
Renovation budget template (CSV)For one room a sheet is the right tool. Past two rooms, or while the dimensions are still moving, the quantities stop following the measurements — which is the whole argument below, and the thing the planner does instead.
Change a room and every quantity re-runs — free to try, nothing to install. What it does that a sheet cannot →
The structure that survives contact with a real job
Most templates fail in the same way: they are a flat list of costs. A renovation is not a flat list. It is several rooms, each with several trades, against one pot of money — and the thing you need to know at any moment is not what it will cost, but whether it is still going to fit.
So the sheet needs eight columns and no more:
| Column | Why it earns its place |
|---|---|
| Room | The unit people actually think and decide in. Cutting a budget means cutting a room, not a percentage. |
| Item | One material or one labour line. Not "bathroom stuff". |
| Unit | m², litres, sheets, packs, days. Mixing units in one column is where most sheets start lying. |
| Qty | What you will buy, waste included — not the area you will cover. |
| Unit price | Per the unit in the column before. Keep it exclusive or inclusive of tax, consistently. |
| Estimated | Qty × unit price, as a formula. Never typed. |
| Actual | Filled from invoices as they arrive. Empty until then — not a guess. |
| Variance | Actual − estimated. The only column that tells you something you did not already know. |
Then a subtotal per room, a contingency line as a percentage of the subtotal, and one total. Contingency as a percentage matters: typed as a round number it stays at £5,000 while the job grows past it.
How much contingency
Ten to twenty per cent, and which end you pick is mostly about whether anything is being opened up. Cosmetic work on a newer house sits near 10%. Once walls, floors or ceilings come open — where rot, wiring and old plumbing are found — 15% to 20% is the honest number. Set it aside at the start and treat it as already spent. A contingency you are willing to dip into for an upgrade is not a contingency; it is a slush fund with a respectable name.
Five things a spreadsheet cannot do
This is not an argument against spreadsheets. It is the list of places where people who budget renovations in them consistently get caught, and it is worth knowing before you are caught rather than after.
- 1Quantities do not follow the dimensions. Change a bathroom from 2.4 m to 2.6 m wide and the tiles, adhesive, grout, membrane and primer all change with it. In a spreadsheet they change only if you remember every line that depended on that number, and work each one out again.
- 2Waste is not one percentage. It depends on the pattern, not the material. A straight-laid tile floor takes roughly 10% extra; herringbone about 15%; a 45-degree diagonal about 17%, because every tile at the edge is a cut. One "add 10%" column quietly under-orders two of those three.
- 3Units do not convert themselves. Paint is sold in tins, tile in square metres, timber in lengths, insulation in packs. The job is measured in none of those. Every row needs a conversion you do yourself, and that is where the rounding errors get in.
- 4Rolling up rooms double-counts. Skip hire, scaffolding and building control belong to the job, not to a room. Spread them across rooms and every room total is wrong; leave them out and the project total is. Most sheets end up doing both at different times.
- 5Estimated against actual drifts apart. The estimate was built in week one and the invoices arrive over three months. Unless something re-reads the estimate each time, the variance column is comparing today’s invoice against a plan nobody has revisited — which is exactly when a budget fails quietly rather than loudly.
When to stop using one
For one room, a spreadsheet is usually the right answer and the template above will do the job. The point it stops working is reliably the same: more than two rooms, or any job where the dimensions are still moving. That is when the arithmetic stops being arithmetic you can redo by hand, and the sheet starts being a record of what you once believed.
That is the point this site exists for. Measure a room once and the quantities fall out of it — with the waste factor for the pattern you actually chose, in the units the material is actually sold in — and the rooms add up to a project total you can hold against what you have really spent.
Common questions
What should a renovation budget spreadsheet include?
One row per material or labour line, grouped by room, with unit, quantity, unit price, estimated cost, actual cost and variance. Add a contingency line as a percentage of the subtotal rather than a round number, so it grows when the job does.
How much contingency should a renovation budget have?
Between 10% and 20% of the total. Around 10% suits cosmetic work on a newer house; 15% to 20% is more realistic once walls, floors or ceilings are opened, because that is when the surprises are found. Set it aside at the start and treat it as spent.
Should quantities in the spreadsheet include waste?
Yes, and it is the most common mistake. Enter the quantity you will buy, not the area you will cover. Tile is the clearest case: a straight-laid floor typically needs about 10% extra, herringbone about 15%, and a 45-degree diagonal about 17% because every edge tile is a cut.
Why does my renovation budget spreadsheet stop adding up?
Almost always because a row was inserted outside a SUM range, or because a quantity changed and the lines that depend on it were not recalculated. A spreadsheet holds numbers but not the relationships between them, so nothing tells you that the adhesive and grout still refer to last week’s floor area.
Is a spreadsheet good enough for a whole-house renovation?
For a single room it is usually fine. It struggles once there are several rooms and trades, because the quantities stop being arithmetic you can redo by hand and the per-room totals have to roll up without double counting shared items like skip hire or scaffolding.
Free to try — no sign-up, nothing to install. What it does that a sheet cannot →