What is the machining cost per part formula?

Cost per Part = (Fixed Setup Cost / Quantity) + Variable Cost per Part. Fixed Setup Cost is the one-time setup, programming, fixturing, and inspection prep; Quantity is the batch size; Variable Cost per Part is machining time times machine rate plus tooling and material per cycle. With $1,200 setup over 200 parts plus $7.40 variable: $6.00 + $7.40 = $13.40 per part.

How do I calculate the variable cost per part?

Multiply cycle time by your machine hour rate, then add per-cycle tooling and material. Keep units aligned: convert cycle time to hours. A 4.0 minute cycle at a $90/hr rate is 0.0667 x $90 = $6.00 in machine cost; add $1.00 tooling and $0.40 material to reach $7.40 per part. Do not mix minutes with an hourly rate, or the machining cost will be off by a factor of 60.

How does batch size affect cost per part?

Only the fixed term changes. With $1,200 setup, the fixed share is $1,200/Quantity: $24.00 at 50 parts, $12.00 at 100, $6.00 at 200, and $2.40 at 500. Add the constant $7.40 variable to each, giving $31.40, $19.40, $13.40, and $9.80 per part. Doubling the batch roughly halves the setup contribution but never touches the $7.40 floor, so gains shrink as quantity grows.

Why is my small-batch price too high to win the job?

Because setup is spread over few parts. That $1,200 over 50 pieces is $24.00 per part, versus $6.00 over 200. If the customer balks, offer a price break at a higher quantity, reduce setup with soft jaws or a preset tool library, or combine the part with a similar job to share fixturing. Do not simply cut price and eat the setup; that turns the run into a loss.

Should setup cost be a separate line or built into the part price?

Both are valid; choose by customer and volume. A separate setup or non-recurring engineering line ($1,200 here) keeps unit price honest across reorders and protects you on small lots. Building it into $/part ($6.00 added at 200 pieces) is cleaner for the buyer but risks the customer reordering 50 at the 200-piece price. For repeat work, a stated setup charge plus a low per-part rate is safest.

What is the difference between cost per part and cost per hour?

Cost per hour is your machine rate, an input, typically $75 to $150/hr covering machine, operator, and overhead. Cost per part is the output of this formula: the rate feeds the Variable Cost per Part term via cycle time, then setup is amortized on top. At a $95/hr rate and 4.5 minute cycle you get $7.13 machining per part, which is only part of the $13.40 total after setup.

Cost and Quoting

Machining Cost per Part Formula

Machining cost per part spreads fixed setup and programming costs across the batch and adds variable machining costs per cycle. Use it when quoting CNC work, comparing lot sizes, or estimating unit cost for a job shop run.

Formula

Cost per Part = (Fixed Setup Cost / Quantity) + Variable Cost per Part

Variables

Fixed Setup Cost: Total setup, programming, fixturing, and inspection prep for the run
Quantity: Number of parts in the batch or quote
Variable Cost per Part: Machining time x machine hour rate plus tooling and material cost per cycle

Understanding the Machining Cost per Part Formula

This formula splits a CNC job into two pieces: a fixed cost you pay once per run and a variable cost you pay per part. Fixed Setup Cost divided by Quantity is how much of the setup each part carries; Variable Cost per Part is the machining, tooling, and material for one cycle. In the example, $1,200 setup over 200 parts is $6.00 per part, plus $7.40 variable, for $13.40. It matters because it shows exactly how batch size drives unit price.

Fixed Setup Cost bundles programming, fixturing, first-article inspection, and physical setup, priced at your labor and engineering rate. Variable Cost per Part is machining time in hours times the machine hour rate, plus per-cycle tooling wear and material. Keep time units consistent: if the rate is $/hour, cycle time must be in hours, so a 4.5 minute cycle at a $95/hr rate is 0.075 x $95 = $7.13. The classic error is quoting one $/part figure without knowing which Quantity it assumes.

Read the two terms separately. As Quantity rises, the fixed-per-part term shrinks toward zero and unit cost approaches the $7.40 variable floor; it can never go below it. At 50 parts the fixed share is $1,200 / 50 = $24.00, giving $31.40 per part, more than double the 200-piece number. Use this to set price breaks: quote a setup surcharge or a tiered table so small lots stay profitable, and flag any request to hold large-batch pricing on a small reorder.

Worked Example

Setup and programming is $1,200. Variable machining cost is $7.40 per part. Batch is 200 parts.

Fixed per part = $1,200 / 200 = $6.00
Total cost per part = $6.00 + $7.40 = $13.40

Result: $13.40 per part

Common Mistake

Quoting the same $/part price for small and large batches. Setup cost spread over 50 parts is four times higher than over 200 parts. Small batches require a tiered price or a clear setup surcharge to be profitable.

Frequently Asked Questions

What is the machining cost per part formula?: Cost per Part = (Fixed Setup Cost / Quantity) + Variable Cost per Part. Fixed Setup Cost is the one-time setup, programming, fixturing, and inspection prep; Quantity is the batch size; Variable Cost per Part is machining time times machine rate plus tooling and material per cycle. With $1,200 setup over 200 parts plus $7.40 variable: $6.00 + $7.40 = $13.40 per part.
How do I calculate the variable cost per part?: Multiply cycle time by your machine hour rate, then add per-cycle tooling and material. Keep units aligned: convert cycle time to hours. A 4.0 minute cycle at a $90/hr rate is 0.0667 x $90 = $6.00 in machine cost; add $1.00 tooling and $0.40 material to reach $7.40 per part. Do not mix minutes with an hourly rate, or the machining cost will be off by a factor of 60.
How does batch size affect cost per part?: Only the fixed term changes. With $1,200 setup, the fixed share is $1,200/Quantity: $24.00 at 50 parts, $12.00 at 100, $6.00 at 200, and $2.40 at 500. Add the constant $7.40 variable to each, giving $31.40, $19.40, $13.40, and $9.80 per part. Doubling the batch roughly halves the setup contribution but never touches the $7.40 floor, so gains shrink as quantity grows.
Why is my small-batch price too high to win the job?: Because setup is spread over few parts. That $1,200 over 50 pieces is $24.00 per part, versus $6.00 over 200. If the customer balks, offer a price break at a higher quantity, reduce setup with soft jaws or a preset tool library, or combine the part with a similar job to share fixturing. Do not simply cut price and eat the setup; that turns the run into a loss.
Should setup cost be a separate line or built into the part price?: Both are valid; choose by customer and volume. A separate setup or non-recurring engineering line ($1,200 here) keeps unit price honest across reorders and protects you on small lots. Building it into $/part ($6.00 added at 200 pieces) is cleaner for the buyer but risks the customer reordering 50 at the 200-piece price. For repeat work, a stated setup charge plus a low per-part rate is safest.
What is the difference between cost per part and cost per hour?: Cost per hour is your machine rate, an input, typically $75 to $150/hr covering machine, operator, and overhead. Cost per part is the output of this formula: the rate feeds the Variable Cost per Part term via cycle time, then setup is amortized on top. At a $95/hr rate and 4.5 minute cycle you get $7.13 machining per part, which is only part of the $13.40 total after setup.