Avoiding Common Estimating Mistakes

The most widespread and damaging mistake. Many tradespeople price materials and labour, then add a margin — without ever accounting for the cost of running the business. Those costs get paid out of profit that was never really there.

• Overheads include vehicle costs, insurance, tools, software, phone, and accounting fees
• These costs exist whether the job runs perfectly or not — they must be recovered from every quote
• Calculate your total monthly overheads, divide by billable hours, and add that figure to every job
• A sole trader running a van typically has £800–£1,500 in monthly overheads before paying themselves anything

If you've never calculated your real monthly overheads, do it this week. Most tradespeople are surprised by how high the number is — and that surprise explains a lot about where the money goes.

Labour estimates almost always go one way: too low. It's human nature to remember the best-case version of a job rather than the realistic one — and clients suffer the consequences when tradespeople rush to make up time.

• Price for your average pace, not your best day — complications are normal, not exceptional
• Include time for site setup, cleanup, client conversations on-site, and tool loading/unloading
• Add travel time both ways — it's part of the job and should be charged accordingly
• Build in a 10–20% contingency for any job where the full scope isn't yet confirmed
• Review completed jobs regularly — if you're consistently over hours, adjust your estimates upward

Material prices change — sometimes dramatically. Quoting from memory or last year's invoice is a reliable way to lose margin on every single job, particularly in periods of supply chain volatility.

• Always get fresh supplier prices for any job over a certain value — set your own threshold
• Update your materials library in QuickEstimate whenever you receive new pricing from suppliers
• For quotes with a long lead time, add a price validity clause to protect against supplier increases
• Be especially careful with timber, steel, pipework, and electrical components — these fluctuate most

A simple clause — "prices valid for 30 days from date of issue" — protects you if material costs rise between quoting and starting work.

Phone and email quotes are tempting — they save time. But jobs quoted without seeing the site carry hidden risks that consistently erode margin: access issues, existing damage, non-standard fittings, and scope that's much larger than described.

• Any job above your minimum threshold should have at least a brief site visit or photo review
• Look specifically for access complications, distances to services, condition of existing work, and parking
• Ask the client directly: has any previous work been done? Are there any known complications?
• If a visit isn't possible, add a larger contingency to the estimate and note assumptions clearly

This is a maths mistake that quietly costs tradespeople thousands of pounds a year. Markup and margin look similar but produce very different results — and confusing the two means you're always earning less than you think.

• A 25% markup on £1,000 of costs gives a sell price of £1,250 — but your margin is only 20%
• If you want a 25% margin, divide your costs by 0.75 — giving a sell price of £1,333
• The higher your target margin, the bigger the gap between markup and margin becomes
• Always use margin-based pricing to ensure you're hitting your actual profit target

Check your last five quotes. If you were applying a markup percentage and calling it a margin, recalculate what you actually earned on those jobs.

Vague quotes invite scope creep — where the job gradually expands beyond what was originally agreed, with no corresponding increase in price. It's one of the most common sources of disputes and lost margin in the trades.

• Define exactly what is included in the price — and be equally explicit about what is not
• Specify materials, brands, or standards where relevant to avoid "can you just upgrade that?" conversations
• State clearly that additional works will be agreed and quoted separately before proceeding
• Use QuickEstimate's scope notes section to attach a written scope directly to every proposal