How to know if your estimates are accurate

You know your estimates are accurate when you compare estimated cost to actual cost on every completed job — and after 20 or 30 jobs, the pattern becomes impossible to miss: which categories you consistently under-bid, which job types quietly lose money, and what your real waste rate is. The catch is the word actual. Most contractors never find out, because the actual costs were never captured while the job ran.

Ask an owner how a job went and you’ll usually get a feeling. The bank account eventually supplies the truth, but by then it’s blended across a dozen jobs and impossible to trace. This guide is the practical version of un-blending it.

Why nobody actually knows

Not because the math is hard — because the inputs are missing. Material comes off the van with no record. The mid-job supply run gets paid on a personal card and forgotten. Small material — fasteners, fittings, consumables — never gets counted at all, on the theory that markup covers it. Labor gets logged, roughly, eventually. Then at tax time the books get squared for the IRS, not for the question “did the Hendersons’ kitchen make money?”

So the estimate and the actual live in two different worlds, and the next bid gets built on the last bid’s gut feel. When owners finally start measuring, the surprises are not small: contractors who assumed a 5% material waste rate have measured closer to 15% once real numbers existed. That’s not a rounding error — on material-heavy work it’s the margin.

The one-page recap habit

The tool is embarrassingly simple. When a job closes, one page, fifteen minutes:

• Materials: bid vs. actual, and the three biggest line items where they differ.
• Labor hours: bid vs. actual, including the trips nobody bid — returns, punch-list visits, the run back for material someone forgot.
• Everything else: dump fees, rentals, subs, permits — the “small stuff” bucket that isn’t.
• One sentence: would you bid this job the same way again?

Ten recaps in, you’ll see it: maybe rough-in always runs true and finish work always runs 20% hot. Maybe one builder’s jobs always sprout unbilled extras. Maybe the $30 supply runs you never counted show up on every single residential job. Twenty or thirty recaps in, your bidding stops being a guess with confidence and becomes a model with evidence.

The recap is only as good as the capture

Here’s where most attempts die: you can’t recap numbers that were never recorded. If actuals get reconstructed at month-end from faded receipts and memory, the recap inherits the fiction. The fix is capturing costs at the moment they happen, with near-zero effort:

• Every purchase gets a job name at the counter — the PO field every supplier offers. (The full system is in our guide to tracking material costs per job.)
• Every pull from stock gets logged as it happens — who took it, which job, how many. Seconds on a phone, or it won’t survive a busy week. (The mechanics: warehouse-to-jobsite tracking.)
• Hours logged same-day, including the unglamorous trips.

And note what doesn’t solve this: your accounting software. QuickBooks sees what got coded, after the fact — it can’t watch material leave a truck. That gap is documented in what QuickBooks can’t do for material job costing.

Common questions