Engineer-to-Order Engineering Hours Estimator
Engineering is usually the least understood line in an engineer-to-order quote, yet it often carries the most schedule and margin risk. This estimator turns a drawing count into hours, cost and elapsed weeks using the same layered logic most ETO estimators keep in a spreadsheet.
Your numbers
Count detail drawings, assemblies, layouts, schematics and P&IDs the job needs, whether new or reused.
Drawings pulled from an earlier job with only dimensional or note changes.
Use your own history. Many shops see roughly 4 to 20 hours for a mix of detail and assembly drawings.
FEA, controls design, calcs, safety review, customer design reviews.
Fully burdened cost rate, not the sell rate.
Your results
Estimating model for budgeting. Calibrate base hours per drawing and the complexity factor against your own closed jobs before using the output in a quote.
Total engineering hours vs share of drawings reused
Sweeps Share of drawings reused or lightly modified from 0 to 95, holding your other inputs fixed.
Calibrate engineering hours from your ERP history
Optional: we review your closed-job hours and suggest base hours per drawing by product family.
Optional. The tool and every export work without this. No spam.
How to use the estimator
Start with the number of drawings and models the job will need, including schematics, layouts and P&IDs, then enter the share you expect to reuse from a prior job. Set the base hours per new drawing from your own history and choose a complexity factor. Add loads for analysis and design review, revisions and project engineering. Enter a burdened rate and the number of engineers to see cost and elapsed weeks. Move the reuse slider to see how much a genuine standard design library is worth on this job.
- Count drawings from a preliminary layout or the nearest similar job
- Use burdened cost rates for cost, sell rates only when pricing
- Record the result next to the actual hours when the job closes
The method behind the numbers
The model is a parametric estimate: a unit of work (equivalent new drawings) multiplied by a historical productivity (hours per drawing) and a complexity factor, then loaded for non-drafting work. Reused drawings are weighted by the effort to adapt them, which is why 100 percent reuse never gives zero hours. Each load is applied to the running subtotal, so revisions are charged on drafting plus analysis, and project engineering is charged on everything before it. Elapsed time is hours divided by team size times 40 hours times utilization, a simple capacity model.
Reading the result and the chart
The primary outputs are total hours and cost. Compare the hours to your last two or three similar jobs: if the estimate sits far outside their actuals, check the drawing count first, then the complexity factor. The chart shows how total hours fall as reuse rises. A shop with a controlled library of standard assemblies will see a steep slope, while a shop that only claims reuse informally will find the real adaptation effort is higher than 15 percent. Use the elapsed weeks output to sanity check the delivery promise.
Common mistakes
The most frequent error is estimating only drafting and forgetting that analysis, customer review cycles and project coordination are real hours. The second is using the standard rate from the quoting system instead of a burdened cost rate. Others include assuming every engineer is productive 100 percent of the time, ignoring that a first-of-a-kind machine does not follow historical hours per drawing, and never feeding actual hours back so the base value improves.
- Do not count reuse unless the source files are findable and current
- Add hours for vendor drawing review and approval cycles
- Re-baseline the base hours per drawing each year
Frequently Asked Questions
What is a reasonable number of hours per drawing?
It varies widely by product. A simple detail drawing can take 2 to 4 hours while a complex weldment or assembly may take 15 to 30. Use your own closed-job data, divide actual engineering hours by final drawing count per product family, and start from that rather than a published number.
Should I include electrical and software engineering?
Yes, if the same team estimates them. Either count schematics, panel layouts and software modules as drawings with their own hours per unit, or run the calculator once per discipline with a different rate and complexity factor, then add the results.
How is design reuse handled?
Reused drawings are weighted by the effort needed to adapt them. At 25 percent, four reused drawings count as one new drawing. This keeps the estimate honest because reuse still needs checking, dimension changes and re-release.
Does this replace a bottom-up estimate?
No. Parametric estimates are quick and useful for early quotes. For a firm fixed-price bid, build a bottom-up task list and use this as a cross-check. A large gap between the two is a signal to review assumptions.
Netray can read closed-job hours from your ERP or PLM and calibrate hours per drawing by product family, so the estimate improves with each job. Ask for a review of your estimating data.
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