Estimate Accuracy Tracker Spreadsheet
A spreadsheet that measures how far your estimates run over, whether it is by the same amount every time, and what to multiply by until they are not.
Everybody knows their estimates run over. Almost nobody knows by how much, or whether it is the same amount every time — and those two answers lead to completely different fixes. One is a multiplier you apply on Monday morning; the other is a conversation about how you estimate.
What is in it
- Setup — three numbers, and one of them is a decision about risk.
- Jobs — 200 rows; five things you type, two of them hours.
- By Estimator — bias and spread kept in separate columns, with a sentence written on each row.
- By Size — where the slip actually lives.
- By Type — when it is a price list problem instead of an estimating one.
- Overview — the whole period on one screen, plus a Start Here tab saying where to type.
Who it is for
Anything quoted before it is done: agencies, software, print, engineering, joinery, translation, events, surveying, garden design, film production. You can estimate in hours, days, money or square metres — put the cost of one of them in Setup and the arithmetic does not care. Thirty jobs is enough to see bias; a hundred is enough to trust the padding.
The worked example
105 finished jobs over eighteen months are filled in, quoted at $338,950. The estimates said 4,681 hours and the work took 5,446.5 — a slip of 16.4% that cost $32,151. A margin quoted at 42.0% was delivered at 32.5%: 9.5 points lost.
87 of the jobs went over at all and 7 went badly out, the worst single one by 79.0%. From that history the file works out a padding of 1.148x, which would have left the studio right or generous on 80.0% of jobs and added $50,165 to those quotes. The 8 jobs over 110 hours were out by 29.6% and carried 54.6% of the whole year’s overrun on their own.
How it works
Compatible with Microsoft Excel 2016 or newer on Windows or Mac, Google Sheets, and LibreOffice. No macros, no add-ons, no account to create, nothing to install.
The download has two workbooks: one with the example above already filled in, so you can see what every column expects, and the same file completely blank for your own figures. A plain-English guide comes as a PDF. Order on WhatsApp — $9
Orders are taken on WhatsApp: message me and I’ll send the payment details, then the files as soon as the payment is confirmed.
A look inside the file
Questions people actually ask
How do I work out how far out my estimates actually are?
Put the hours you said against the hours it took, job by job, and the file separates the two ways an estimate is wrong: bias, being out in the same direction by roughly the same amount, and spread, being out by a different amount every time. In the worked eighteen months 105 finished jobs quoted 4,681 hours and took 5,446.5 — a 16.4% slip that cost $32,151 and turned a quoted 42.0% margin into 32.5%. Big jobs are where it lives: eight jobs over 110 hours were out by 29.6% and caused 54.6% of the damage.
Is this only for fit-out and construction, and what if we estimate in days or money rather than hours?
No — it fits anything quoted before it is done: agencies, software, print, engineering, joinery, translation, events, surveying, garden design, film production. Use whatever unit you estimate in and put the cost of one of them in Setup; the arithmetic does not care whether it is an hour, a day or a square metre.
How many finished jobs do I need before it tells me anything?
Thirty is enough to see bias and a hundred is enough to trust the padding, so start with whatever you can find and the file gets more useful every month. Five things go in per job across 200 rows, two of them hours. From your own history it works the multiplier out again every time you add a job: 1.148x in the worked file, which would have left you right or generous on 80% of jobs and added $50,165 to those quotes.
Does it work in Google Sheets, and do I need a subscription?
Yes — the file is built as .xlsx, so it opens in Excel 2016 or newer on Windows or Mac, goes into Google Sheets through File → Import → Upload, and works in LibreOffice. No macros, no add-ons, no account to create, nothing to install and no subscription. You download a file and it is yours. Two hundred job rows, with the worked eighteen months filled in, a blank copy carrying the same formulas, and a plain-English PDF guide.
Will it embarrass whoever wrote the estimate?
It does name the estimator on each job — that is the point of the By Estimator tab — and it says on the page that being out by the same amount every time is the most useful information in the building, because it is fixed with a multiplier by Monday. It is not a time tracking or timesheet system, not a quoting, proposal or CRM tool, not a project plan, and nothing syncs or logs in. It will not make your estimates better; it tells you exactly how they are wrong and what to multiply by until they are not.
Need it built around your business?
This one assumes jobs estimated in hours by a named estimator. If yours is different — estimating in square metres or tonnes, quotes built from a rate card rather than from time, or several trades on one job each pricing their own part — I can build the same bias and spread arithmetic around your own unit.
All other templates are listed on the Excel & Google Sheets Templates page.