how to quote a job (without losing your shirt)

Most contractors have lost money on a job. Not because they did bad work — because they quoted wrong. They priced based on best-case thinking, got the job, then watched their margin evaporate when reality showed up.

This guide explains why that happens, and how to fix it with a method that takes about five minutes longer than your current approach.

why contractors underquote

Three forces push every quote downward:

Optimism bias. You picture the job going smoothly. The plaster comes off clean. The joists are solid. The supplier delivers on time. You price for the version of the job where nothing goes wrong — even though that version almost never happens.

Competitive pressure. You know the customer has three quotes. So you sharpen your pencil, trim the fat, round everything down. Now your quote is tight. Too tight. You win the job and lose the profit.

Single-point estimates. You write down one number for each line item: tiles £2,000. That is not an estimate. That is a guess dressed up as a fact. Real costs are ranges. Tiles could be £1,800 if your usual supplier has stock, or £2,400 if they do not and you are ordering from someone new.

the five uncertainty tiers

Not every line item in your quote carries the same risk. A skip hire from the company you have used fifty times is not the same as a custom glass shower screen from a fabricator you found last week. Treating them the same is the core mistake in flat contingency pricing.

LowRiskQuotes uses five tiers of uncertainty. Here is what each one means in practice:

The key question for each line item is: how confident am I that this number is right? Not how confident you want to be. How confident you actually are, based on evidence. Have you got a written quote? That is Certain. Are you guessing from a job you did two years ago in a different postcode? That is High at best.

worked example: bathroom renovation

Let us walk through a real quote. Mrs. Chen wants her bathroom redone — strip out, re-tile, new fixtures, custom glass shower screen, new plumbing, electrics, and a skip for the waste. Your base estimate comes to £6,400.

If you quoted £6,400 flat, you are pricing for the scenario where every single line item comes in exactly on estimate. That is the single most unlikely outcome. It is like betting that every coin in a six-coin toss lands heads.

Run those numbers through a Monte Carlo simulation and you get a distribution. The simulation runs thousands of versions of this job, each time pulling costs from within the uncertainty range you set. Because overruns are more common than underruns, the simulation skews upward — just like real life.

The difference between £6,400 and £7,180 is £780 — about 12%. But it is not a flat 12% contingency. It is a calculated buffer based on the specific risks in this specific job. A job with all-Low items would need less. A job full of Wild Guesses would need much more.

reading the results: what the bell curve means

The simulation gives you a probability distribution — a bell curve showing how likely each total cost is. Here is how to read it:

• P50 means there is a 50% chance the actual cost is below this number. Coin-flip odds. Not a safe quote.
• P80 means 80% chance the actual cost is below this. This is the sweet spot for most contractors. You are protected against most overruns without pricing yourself out of the market.
• P95 means 95% chance. This is your "sleep well at night" number. Use it for fixed-price contracts or customers who will not accept any variation.

Which percentile you quote at depends on the job and the customer. A time-and-materials job with a good client? P50 might be fine. A fixed-price kitchen for a solicitor who will hold you to every penny? Quote at P80 or P95 and protect yourself.

common quoting mistakes

After running thousands of estimates through the simulator, patterns emerge. Here are the mistakes that cost contractors the most money:

1. Marking everything as Low uncertainty. If you have not got a written quote, it is not Low. If you have not done this exact scope before, it is not Low. Be honest with yourself.
2. Forgetting travel and time costs. Two hours of driving per day at £30/hour for a three-week job is £900. That is real money. Price it.
3. Not pricing for delays. Weather, late deliveries, customer changes. These are not rare events. They are the norm. Your job duration estimate needs its own uncertainty tier.
4. Copying last year's prices. Material costs move. Timber is up. Copper is up. If your prices are six months old, they are wrong.
5. Quoting to win instead of quoting to profit. A job you win at the wrong price is worse than a job you do not get. The worst outcome is not losing the bid. It is winning it and working for free.

putting it together

Here is the workflow. It adds about five minutes to your quoting process:

1. List every line item as you normally would.
2. For each one, ask: how confident am I in this number? Assign a tier.
3. Add your daily rate, job duration, and travel.
4. Run the simulation.
5. Quote at P80 for most jobs. Adjust up or down based on contract type.

You are not adding a made-up contingency. You are building a quote that reflects the actual risk profile of the actual job. That is the difference between hoping you make money and knowing you will.