Most contractors don't lose money because their work is bad — they lose it on the estimate, weeks before the first nail is driven. The same estimating errors show up over and over: underestimated labor hours, missing overhead, the margin vs markup mix-up, missing waste factor, and change order failures. This guide gives you a practical fix for each one.
Labor hours are the hardest line item to estimate and the easiest to get wrong. Most contractors track estimated vs actual hours on fewer than half their jobs, which means they never build accurate correction factors. Fix: log actual hours on every job for 90 days and compare to your estimates. You will find systematic patterns — specific task types you consistently underestimate by 20–40%.
Adding 30% markup on a $10,000 cost gives you $13,000 revenue — but your gross margin is only 23.1%, not 30%. If you target 30% margin, you need to add 42.9% markup. Mixing these up on a year of $500,000 revenue means $34,500 in lost gross profit. Fix: always apply markup, always report margin — use a conversion table or the EstiDash margin calculator.
Waste factor (5–15% on most materials), permit fees ($50–$500+), and windshield time (unpaid travel between jobs) are easy to forget and brutal to absorb after the fact. A roofer spending 45 minutes per day on travel loses 180+ billable hours per year. Fix: add overhead as standard line items in every estimate template — never calculate them ad hoc.
Material prices can move 15–30% in six months on volatile commodities (lumber, copper wire, steel). An estimate built on six-month-old prices on a $40,000 material-heavy job can be $6,000–$12,000 short before a single hour of labor is worked. Fix: pull fresh supplier quotes for any major material category within 2 weeks of submitting a bid.
Every estimate should list scope assumptions, exclusions, and material allowances in writing. Without documentation, every ambiguity becomes a dispute — and disputes always cost time and goodwill. Fix: use a standard estimate template that forces you to list what is and is not included. Price every change order before doing the work, not after.