It feels like the cheaper option: price the job yourself, save the fee, submit the tender. When you weigh up a rough estimate vs proper estimate, the rough one always looks free. The maths only works out that way if the rough estimate turns out to be right, and on the jobs that go wrong, it usually wasn't.
Nobody sets out to produce a bad estimate. The rough one happens because there isn't time, the job looks straightforward, and you've done plenty like it before. It's a reasonable decision on the night. The bill for it arrives later.
A missed line costs more than a measured takeoff
One item left off a rough estimate (a preliminary, a small quantity, a piece of work between trades) comes straight out of your margin on site. There's no client to pass it on to. You priced the job, they accepted the price, and the missing line is yours.
Here's a simple, hypothetical example. Say you win a job at £60,000 with a 10% margin built in, so you're expecting £6,000 profit. Somewhere in the rough estimate, a drainage run and the making good around it were missed, and they cost £3,000 to put right. Half your profit has gone on one line. Miss two lines like that and you've built the job for nothing.
That single missed line frequently costs more than the fee for having the job measured properly in the first place. Not because the fee is small, but because missed lines on a real job are rarely small either.
A guessed rate is a bet in the wrong direction
Missing items is one risk. Guessing rates is the other, and it cuts both ways.
Guess a rate too low and you're carrying the difference yourself, on every unit of that item across the whole job. Guess it too high and you lose the bid entirely, often without ever knowing why. The rough estimate doesn't tell you which of those is happening. It just produces a number.
Rates drift, too. The figure you paid for a job last year, or the year before, may not be what it costs now. Materials move, labour moves, and a rate that was right on your last extension can be quietly wrong on this one. Using remembered rates is one of the most common ways a rough estimate goes wrong without anyone noticing until the invoices come in.
A measured estimate priced on current rates, local to the job, takes the guessing out of both sides of that bet. You still decide your margin. You just decide it on top of a cost you can trust.
A rough estimate isn't cheaper. It's a proper estimate with the cost deferred until you're on site and can't do anything about it.
Rough estimate vs proper estimate, line by line
The difference isn't the total. It's what sits underneath it. Put the two side by side and it looks like this:
- Quantities. The rough estimate has lump sums and round numbers. The proper one has every element measured off the drawings to NRM2.
- Rates. Rough: whatever you paid last time, adjusted by feel. Proper: current UK rates for the job's location.
- Assumptions. Rough: held in your head, if anywhere. Proper: written down, so you and the client both know what's included.
- Variations. Rough: nothing to price a change against. Proper: a measured baseline for every change the client asks for.
- Credibility. Rough: one figure the client has to take on trust. Proper: a breakdown they can check.
Each of those differences costs something when it goes wrong. The rough estimate doesn't avoid those costs. It just doesn't show them until later.
The fee is the cost of certainty, not an extra
Paying for a proper estimate isn't an added cost on top of the job. It's the cost of knowing the number is right before you commit to it, rather than finding out after you've already won the job.
There's also the time. A rough estimate isn't free even if you do it yourself. It costs evenings, and it costs them at exactly the point when you're tired and trying to run the job you've already got. If you've ever compared an estimating service with your own guesswork, you'll know the biggest difference often isn't the price. It's how confident you feel submitting it.
At MPE the fee is fixed and agreed up front, so you know exactly what certainty costs before you commit. Every element is measured off your drawings to NRM2, priced on current rates local to the job, and delivered before your deadline.
When a rough figure is fine
There's a place for rough numbers. Early conversations with a client, before there are drawings, need a ballpark to see whether the project is realistic at all. A quick feasibility check is exactly what a rough figure is for.
The problem starts when the rough figure becomes the tender. Once you're committing to a price, with your name on it and your margin inside it, the job needs measuring.
A useful habit is to label rough figures clearly as what they are. "Budget estimate, subject to drawings and measurement" on a ballpark number protects you from being held to it later. Then, when the drawings arrive and the client wants a firm price, you produce the proper one.
The one-line test
Before you submit a rough price, look at the job and ask: what's the most expensive single item I could have missed? A drainage run, a steel, a length of retaining wall, the scaffold. If the cost of that one item is more than the fee for a proper estimate, you already have your answer on rough estimate vs proper estimate.