How to Calculate CNC Machine Rate
Machine rate is not a price list. It is a build-up of machine cost, labor, floor overhead and scrap, divided by the hours you can actually bill. This guide walks through the arithmetic, then shows where a quoted number usually hides extra cost.
Key takeaways
How to calculate CNC machine rate per billable hour
Start with what the machine costs you every month, whether it runs or not. Include the lease or depreciation payment, the floor space it sits on, power, compressed air, coolant and the maintenance contract. A 5-axis machining center with a Ø400 mm rotary table draws more power and needs more floor area than a 3-axis mill, so its monthly fixed cost is higher even at idle.
Divide that monthly number by billable spindle hours, not calendar hours. A machine can be powered on 700 hours a month, but if programming, setup, waiting for material and inspection eat half the time, only about 350 hours go to cutting metal. Using 700 makes your rate look cheap and your jobs lose money.
Add direct labor for the operator who tends the machine, plus a share of indirect labor: programming, scheduling, quality inspection and shipping. If one programmer supports four machines, each machine carries a quarter of that salary. The same logic applies to the CMM operator and the person who packs the parts.
The last piece is a scrap and rework allowance. Add it as a percentage that reflects the real difficulty of the part, not a flat number. A simple bracket in 6061 may run near zero; a thin-wall 7075 housing held at ±0.005 mm will not. Keep it visible in the calculation so nobody forgets it exists.
How to estimate cycle time before you trust a rate
Rate means nothing until you know how many minutes the part occupies the spindle. Estimate per feature, not per part. A face mill pass, a pocket, a drilled hole, a tapped hole and a profile cut each have their own time. Add them, then add tool changes and rapids between them.
Use cutting data you can defend. In 6061-T6 aluminum, a 12 mm carbide end mill at 0.05 mm per tooth and 8,000 rpm removes material fast. The same tool in 17-4PH stainless runs far slower and eats inserts. Material choice can double or triple the cycle time before geometry even enters the discussion.
Tolerance and finish add passes. Holding ±0.005 mm usually means a semi-finish pass, a finish pass and a spring pass on critical walls. If the print calls for Ra 0.2–0.8 μm, plan for a separate finishing tool and a slower feed. A part machined to Ra 1.6–3.2 μm can often skip that step.
Then check the number against reality. Cut the air, run one part, and time it. If your estimate says 18 minutes and the machine says 26, the estimate is wrong, and every quote built on it is wrong too. Fix the estimate before you argue about the hourly rate.
What a simple rate formula leaves out
Most first-pass calculations look like this: machine cost plus labor, divided by hours, multiplied by cycle time. That is a fair starting point. It just never survives contact with a real part. The gaps show up later as margin loss, and they are predictable.
Setup is the biggest omission. A first article on a 5-axis job can take two to four hours: fixtures, work offsets, probing, and a trial cut. On a run of 5,000 parts that cost disappears. On a run of five parts, it dominates the price. This is why lot size changes the answer more than the machine does.
Tooling is the second gap. Carbide inserts, custom form tools, reamers and a fixture plate are real money. Some can be amortized; some are consumed by the job. Either way they belong in the quote as their own line, not folded into an hourly figure that nobody can audit later.
Inspection and finishing are the third. A 100% inspection requirement adds CMM time per part. Anodizing, electroless nickel or black oxide adds outside processing, packing and a second shipping leg. If the drawing mentions any of these, the rate calculation must mention them too.
Step by step: build the rate and the part price
Follow the order. Changing it produces a number that looks fine and prices nothing.
- 1Collect fixed monthly costLease or depreciation, floor space, power, air, coolant and maintenance for one machine. Keep it to that machine, not the whole shop.
- 2Count billable spindle hoursTake powered-on hours and subtract programming, setup, waiting and inspection. Typical utilization lands between 45% and 60%.
- 3Add direct and indirect laborOperator time for the machine, plus a fair share of programming, quality and shipping. Allocate by machine, not by headcount.
- 4Divide to get the hourly rateFixed monthly cost plus monthly labor, divided by billable hours. This is your cost, before margin and before scrap.
- 5Estimate cycle time per featureFace, pocket, drill, tap, profile. Add tool changes. Use cutting data matched to the material, from 6061 to Inconel.
- 6Add setup, tooling and inspectionSetup hours divided by lot size, plus consumable tooling, plus inspection minutes per part. Keep each as a visible line.
- 7Apply scrap allowance and marginA small percentage for simple parts, more for tight-tolerance or thin-wall work. Then add margin. Never mix the two.
- 8Sanity-check against a real cutRun one part and time it. If actual time beats the estimate by more than 15%, fix the estimate before quoting.
Cost items and where they belong in the calculation
Use this to see what a bare hourly rate formula misses.
| Cost item | Fixed or variable | Driven by | If omitted |
|---|---|---|---|
| Machine depreciation or lease | Fixed | Machine class and age | Rate looks low, margin disappears |
| Floor space and power | Fixed | Footprint and spindle load | Overhead lands on other jobs |
| Operator labor | Variable | Cycle time and manning | Price ignores the real bottleneck |
| Setup and first article | Fixed per lot | Part complexity, fixture count | Small lots quoted far too cheap |
| Consumable tooling | Variable | Material and feature count | Insert cost eats the margin |
| Inspection and CMM time | Variable | Tolerance and print notes | Quality work becomes unpaid work |
| Outside finishing | Variable | Anodize, plating, coating | Freight and handling appear late |
| Scrap and rework | Variable | Tolerance, wall thickness | Losses are absorbed, not priced |
Frequently asked questions
Should the hourly rate include profit?
No. Build the rate from cost only, then apply margin to the job. Mixing them means you cannot tell whether a low quote came from an efficient process or from a thin margin, and you cannot renegotiate either one later.
How do I handle a one-off prototype?
Put setup, programming and fixture time on the quote as separate lines. On a single part they can be larger than the cutting time. That is normal, and hiding it only creates a surprise when the production quote arrives.
Does a 5-axis machine always cost more per hour?
Its fixed cost is higher, but the part price may be lower. One 5-axis setup can replace three 3-axis setups on a complex housing, which removes handling and re-fixturing error. Compare total part cost, not hourly rate.
How much scrap allowance is normal?
It depends on the part, not the shop. A simple 6061 bracket needs almost none. A thin-wall 7075 or titanium part held at ±0.005 mm with a fine Ra 0.2–0.8 μm finish needs a real allowance, and it should be itemized.
Why do two suppliers give very different rates?
Usually different utilization assumptions and different overhead allocation. One shop spreads cost across many machines; another spreads it across the machines that actually run the job. Ask what billable hours the rate is based on.
What data should I send for a firm quote?
STEP or native CAD, 2D prints with tolerances and finish callouts, material grade, quantity and any inspection or certification requirement. Missing finish or inspection notes are the most common cause of a revised price.
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