CNC Machining Time and Lot Quote Check Calculator
Calculate cutting time per operation from spindle speed, feed and path length, then add setup, tool changes and loading for the lot.
Check whether quantity-break quotes and lead times agree with the confirmed cutting conditions and save a worksheet for the shop.
n = vc×1000/(π×D); milling vf = fz×zc×n; turning and drilling vf = fn×n; cutting time = path length ÷ vf. Enter the cutting conditions and path lengths confirmed by the shop or CAM to check whether the quoted times and quantity breaks agree.
It does not recommend cutting data, generate G-code, approve tool or machine safety, or quote from drawings. Acceleration, tool wear and corner slow-downs enter only through non-cutting time and the allowance.
These inputs began with a fictional aluminium bracket example. Replace them with your quote and CAM path values. Example values are not recommended cutting data or market prices.
1. Cutting conditions and toolpath by operation
For each operation enter the confirmed rpm directly or derive it from cutting speed vc and diameter. Path length is the per-pass cutting length from CAM or the shop; for drilling add approach and breakthrough to the hole depth.
2. Lot quantity and non-cutting time
Blank items are unconfirmed, counted as zero and listed in the omissions table. Setup repeats on each machine; enter an allowance only if agreed with the shop.
Applied to the whole cycle. Default 0%
Leave blank to skip the check
3. Quoted prices, times and lead time
Use the hourly rate stated by the shop. If quoted unit prices include material or finishing, enter that amount as other cost per part so only machining time is compared.
Quantity-break quotes (up to 6)
Lead-time check
Check results
Some items need confirmation
- Some quantity-break prices are below the per-part cycle cost floor. Check the hourly rate, missing operations and lead time.
- Some quantity-break quotes fall outside the tolerance. Ask for the operation and setup basis behind the gap.
- The per-part time implied by the quote structure is shorter than the pure cutting time. The price structure is hard to achieve under the confirmed conditions.
- Cycle per part
- 8.26 min
- Cutting 6.36 min · non-cutting 1.90 min
- Lot total time
- 8.88 h
- 532.99 min · fixed 120.00 min
- Lot machining cost
- 532,994 KRW
- Estimated unit price 13,660 KRW
- Cutting share
- 77.0%
- Share of the cycle spent cutting
Cutting time by operation
| Operation / type | rpm | vc (m/min) | vf (mm/min) | Per part (min) | Lot (min) |
|---|---|---|---|---|---|
| Top face milling Milling (end mill or face mill) | 3,000 | 471.2 | 1,200.0 | 1.00 | 50.00 |
| Pocket end milling Milling (end mill or face mill) | 4,775 | 150.0 | 477.5 | 5.03 | 251.33 |
| Ø8 through holes Drilling (holes) | 2,000 | 50.3 | 300.0 | 0.33 | 16.67 |
Non-cutting omissions table
| Item | Status | Time counted (min) |
|---|---|---|
| Setup (per lot and machine) | Entered | 90.00 |
| First-article inspection and prove-out (per lot) | Entered | 30.00 |
| Tool changes (per part) | Entered | 0.40 |
| Loading and unloading (per part) | Entered | 1.00 |
| Rapid moves and air cutting (per part) | Entered | 0.50 |
| Allowance (acceleration, wear, etc.) | Zero · check the quote | 0.00 |
Quoted time comparison
- Quoted per part 9.00 min vs calculated cycle 8.26 min (+8.96%)
- Quoted fixed time 120.00 min vs entered setup × machines + inspection 120.00 min (0.00 min)
- Quoted lot time 570.00 min vs calculated 532.99 min (+6.94%)
Quantity-break comparison
| Verdict | Quantity | Quote, comparable (KRW) | Estimate (KRW) | Difference (KRW) | Difference | Implied time (min/part) |
|---|---|---|---|---|---|---|
| Quote higher · ask for basis | 10 | 32,000 | 23,260 | +8,740 | +37.58% | 29.00 |
| Consistent | 50 | 15,000 | 13,660 | +1,340 | +9.81% | 12.00 |
| Quote lower · check omissions and lead time Below cycle cost floor | 100 | 11,000 | 12,460 | -1,460 | -11.72% | 8.00 |
Cycle cost floor = cycle per part × hourly rate = 8,260 KRW
Implied quote structure (least-squares line)
Fitting lot total = fixed + per-part × quantity gives fixed 264,754 KRW (264.75 min), per part 8,598 KRW (excluding other cost 5.60 min).
Calculated fixed time 120.00 min · calculated cycle 8.26 min · cutting 6.36 min
Lead-time check
Required working days 2 / quoted lead time 2 · fits within machine time
Material procurement, heat treatment, plating, external inspection and shipping waits are not included.
What you miss when you only look at cutting time in a CNC quote
An outsourced CNC quote states a time per part and a unit price, but rarely shows how that time was built.
If you calculate only the pure cutting time and compare it with the quote, setup, tool changes, loading and first-article inspection drop out and the quote can look inflated.
The opposite mistake is accepting a low quote or a short lead time that ignores non-cutting time, which leads to requotes, late deliveries and quality problems.
The CNC Machining Time and Lot Quote Check Calculator uses the spindle speed, feed and path length confirmed by the shop to calculate pure cutting time for milling, turning and drilling.
It then adds per-lot setup and per-part non-cutting time separately to get the lot total time and machining cost, and checks whether the quoted time, quantity-break prices and lead time are consistent.
You can save the result as a worksheet to ask the shop for its toolpath and setup basis.
This calculator is based on Korean rules for VAT and outsourcing contracts as of 2026, with prices in KRW.
The cutting formulas themselves are international and apply to any machine shop.
Who it helps
- Owners of part machining or repair businesses who send the same drawing to several shops and compare times and lot prices
- Development engineers checking whether the gap between a 10-piece prototype quote and a 100-piece production quote is explained by spreading setup
- Workshop and small-factory operators who want to estimate lot time and lead time on their own machines before quoting
Main features from operation time to quote checks
Cutting time by operation
Choose milling, turning or drilling for each operation and enter the confirmed rpm or cutting speed vc.
Milling uses feed per tooth and effective teeth, while turning and drilling use feed per revolution, to get the feed rate; path length, passes and identical features then give the time per part.
Up to 12 operations can be added for one part.
Non-cutting omissions table
Setup, first-article inspection, tool changes, loading, rapid moves and air cutting, and the allowance are each marked as entered, zero or unconfirmed.
Blank items are counted as zero minutes but stay listed as unconfirmed so you can ask whether the quote includes them.
Setup is repeated for each machine assigned.
Quantity-break checks and implied structure
Up to six quantity-break prices are compared with the calculated unit price and marked consistent, quote higher or quote lower.
The table also flags prices below the per-part cycle cost floor and shows the fixed and per-part time implied by a least-squares line.
Lead-time check and worksheet
Operating hours per day and the number of machines give the required working days, which are compared with the quoted lead time.
A TXT worksheet with operation times, non-cutting status, quote checks and items to confirm is saved directly in your browser; no input is sent to a server.
Match the meaning and units of each input first
- Spindle speed and cutting speed: Confirmed rpm is the spindle speed in the shop’s program.
Cutting speed vc is in m/min and is converted to rpm together with the diameter.
If you enter a machine maximum rpm, any derived rpm above that limit is capped at the maximum.
A confirmed rpm above the maximum is kept as entered and flagged for confirmation. - Diameter: Use the actual cutting diameter at depth for milling (Dcap), the machined diameter for turning (Dm) and the drill diameter for drilling (Dc).
For tools whose effective diameter changes with depth, such as ball-nose end mills, confirm the value the shop used. - Feed: For milling enter feed per tooth fz (mm/tooth) and the effective teeth zc that actually engage.
For turning and drilling enter feed per revolution fn (mm/rev), and do not confuse it with a table feed in mm/min. - Path length, passes and identical features: Path length is the per-pass cutting length in mm from CAM.
Repeat roughing and finishing over the same length with passes, and four identical holes with identical features.
For drilling add the approach distance and breakthrough allowance to the hole depth. - Hourly rate and other cost: The hourly rate is the KRW per hour stated by the shop; no market average is built in.
If quoted unit prices include material or finishing, enter that amount as other cost per part so that only machining time is compared.
Cutting formulas and lot time equations
Spindle speed, feed rate and cutting time
n = vc × 1000 ÷ (π × D)
Milling vf = fz × zc × n
Turning and drilling vf = fn × n
Operation cutting time (min/part) = path length × passes × identical features ÷ vf
All three processes divide path length by the feed rate per minute.
The turning machining time Tc = lm ÷ (fn × n) is the same equation with vf = fn × n substituted.
The formulas were checked on October 24, 2026 (2026-10-24) against the milling, turning and drilling technical pages of tool maker Sandvik Coromant.
Cycle, lot time and machining cost
Non-cutting (min/part) = (tool change s × changes per part + loading s + rapid/air cutting s) ÷ 60
Cycle (min/part) = (cutting + non-cutting) × (1 + allowance ÷ 100)
Lot time (min) = setup × machines + first-article inspection + quantity × cycle
Estimated unit price(q) = lot time(q) ÷ 60 × hourly rate ÷ q + other cost per part
| Symbol | Meaning | Unit |
|---|---|---|
| n | Spindle speed | rpm |
| vc | Cutting speed | m/min |
| D (Dcap, Dm, Dc) | Milling cutting diameter, turning machined diameter, drill diameter | mm |
| fz | Feed per tooth (milling) | mm/tooth |
| zc | Effective teeth (milling) | count |
| fn | Feed per revolution (turning, drilling) | mm/rev |
| vf | Feed rate per minute | mm/min |
| lm | Path length × passes × identical features | mm |
Step-by-step use
- From the quote or CAM sheet, confirm the operation sequence and, for each operation, the tool diameter, spindle speed or cutting speed, feed and path length.
Do not guess unconfirmed values; ask the shop. - Add operation rows, choose the type and enter the values.
Use identical features for repeated shapes and passes for repeated roughing and finishing. - Enter the order quantity and the setup, first-article inspection, tool change, loading and rapid move times.
Enter an allowance only if you agreed one with the shop. - Enter the hourly rate, other cost, VAT basis, quoted setup and time per part, then add the quantity-break prices.
To check delivery, also fill in operating hours per day, machines and the quoted lead time. - Read the items to confirm and the omissions table, then save the TXT worksheet.
Send it to the shop, confirm the basis for any operation or setup gaps, and then fix the lot quantity and place the order.
A fictional example checked by hand
A lot of 50 aluminium brackets
The three operations take 1.00, 5.03 and 0.33 minutes of pure cutting per part, 6.36 minutes in total.
Tool changes of 8 s × 3, 60 s of loading and 30 s of rapid moves add 1.90 minutes of non-cutting time, giving a cycle of 8.26 minutes per part with a 77.0% cutting share.
Adding 90 minutes of setup and 30 minutes of first-article inspection gives a lot total of 532.99 minutes, or 8.88 hours.
At KRW 60,000 per hour the lot machining cost is KRW 532,994, and with KRW 3,000 of other cost per part the estimated unit price is KRW 13,660.
These are fictional values checked with the pure functions in the code, not recommended cutting data or market prices.
| Operation | vf (mm/min) | Per part (min) |
|---|---|---|
| Milling 1 · top face (3,000rpm, fz 0.1, 4 teeth) | 1,200.0 | 1.00 |
| Milling 2 · pocket (vc 150, Ø10 → 4,775rpm, 2 teeth) | 477.5 | 5.03 |
| Drilling · four Ø8 holes (2,000rpm, fn 0.15) | 300.0 | 0.33 |
Quantity breaks and quoted time
With a quoted setup and inspection time of 120 minutes and 9.0 minutes per part, the quoted lot time is 570 minutes, 6.94% longer than calculated.
If the quantity breaks are 10 pieces at KRW 32,000, 50 at KRW 15,000 and 100 at KRW 11,000 (VAT excluded), the 10-piece price is 37.58% above the KRW 23,260 estimate and the 50-piece price is 9.81% above KRW 13,660, consistent within the 10% tolerance.
The 100-piece price is 11.72% below the KRW 12,460 estimate, and KRW 8,000 after other cost is below the cycle cost floor of KRW 8,260.
Fitting a line through the three quotes implies 264.75 minutes of fixed time and 5.60 minutes per part, shorter than the 6.36 minutes of cutting, so the structure is flagged as hard to achieve under the confirmed conditions.
At 8 hours on one machine the lot needs 2 working days, within the quoted lead time of 2 days.
How to read the quote check
When the quote is higher
A small-lot quote far above the calculation may include longer setup, a minimum charge, fixture making or programming fees.
If the implied fixed part is much larger than your entered setup, ask the shop to itemise where the per-lot cost goes.
These can be legitimate costs, so a gap alone does not prove an excessive quote.
When the quote is lower
A unit price below the cycle cost floor means the confirmed cutting data and hourly rate do not even recover the machine time per part.
Find out whether an operation was dropped, faster cutting data or a different machine is assumed, or the material supply terms differ.
A negative implied fixed part means a volume discount larger than spreading setup, so recheck the quantity pricing.
The cutting share is the portion of the cycle in which the tool is actually cutting.
When it is low, reducing non-cutting time through fewer setups, multi-part fixturing or better tool organisation can matter more than changing cutting data.
Three practical situations
Comparing several shops on one basis
When shops use different hourly rates and setup rules, unit prices alone are hard to compare.
Keep the same operation inputs and swap in each shop’s hourly rate and prices to see which one loads cost into setup and which into time per part.
Moving from prototype to production
Check whether the difference between a 10-piece prototype quote and a 100-piece production quote is explained by spreading setup.
If the implied per-part time is close to the calculated cycle, the discount is reasonable; if not, ask whether production fixtures or process changes are assumed.
When a tight lead time is promised
If the required working days, lot total time divided by operating hours and machines, exceed the quoted lead time, more machines or split deliveries are needed.
Finishing and shipping are separate, so confirm the real arrival date against the shop’s production plan.
Contract and tax checks before outsourcing in Korea
Article 3 of Korea’s Fair Transactions in Subcontracting Act (MST 288625, effective 2026-10-02) requires a covered principal contractor that entrusts manufacturing to issue a written contract stating the subcontract price and payment method before the subcontractor starts work.
Article 4 of the same Act treats uniform price cuts without justification and unilaterally low prices as unfair price setting.
Whether the Act applies depends on the size requirements for both parties, so check guidance from the Korea Fair Trade Commission or a professional.
- Do not use these results to demand a unilateral price cut; use them as material to discuss the basis of the operation and time gaps.
- Under Article 30 of the Value-Added Tax Act (MST 276117, effective 2026-01-02) the VAT rate is 10%, so VAT-inclusive quotes are divided by 1.1 for a like-for-like comparison.
- If operations or quantities change through additional or modified orders, recalculate the worksheet and record the change in writing.
Limits of the calculation and tips for checking quotes
The formulas give an ideal time that assumes the feed rate is held constant.
Real machines take longer because of acceleration, corner slow-downs, tool wear compensation, peck drilling retracts and measurement stops.
These differences enter only through the non-cutting time and allowance you agree with the shop, and the calculator does not recommend cutting data, generate G-code, approve tool or machine safety, or quote from drawings.
- Get path lengths from CAM output instead of estimating them from the drawing.
Estimated paths are often too short and make a quote look excessive. - Confirm whether setup repeats on each machine and whether first-article inspection is needed for every lot.
Split deliveries can add more than one setup. - Ask whether the hourly rate already includes tooling, power and programming, and avoid counting them twice.
- Enter the machine maximum rpm to check that small tools do not exceed the spindle limit.
If the cap applies, the real time is longer than the uncapped calculation.
Frequently asked questions
Can I compare a quote with pure cutting time alone?
Pure cutting time covers only the time the tool is feeding and removing material.
A machining quote also carries setup, first-article inspection, tool changes, loading and rapid moves, none of which produce chips.
On small lots these non-cutting items often exceed cutting time, so compare every row of the omissions table with the quote.
What is the difference between entering rpm and cutting speed vc?
If the shop told you the spindle speed in its program, entering that rpm is the most accurate choice.
If you only have a cutting speed vc from the shop or a tool catalogue, the calculator converts it with n = vc × 1000 ÷ (π × D).
A wrong diameter distorts both rpm and time, so use the cutting diameter for milling, the machined diameter for turning and the drill diameter for drilling.
Does this calculator recommend cutting data?
No.
Suitable conditions depend on material, tool coating, fixturing rigidity and machine power, so it never produces recommended values.
It only checks whether the conditions confirmed by the shop or written on a CAM sheet agree with the quoted time, and it does not replace tool or machine safety approval.
How do I enter a facing cut where the diameter keeps changing?
With constant surface speed (G96), spindle speed changes continuously as the diameter shrinks.
This calculator takes one diameter per operation, so approximate with the average machined diameter or an average rpm confirmed by the shop.
Near the centre the spindle may hit its maximum rpm and the real time grows, so fill in the machine maximum rpm to see whether the cap applies.
What does the implied quote structure mean?
Quoted unit prices for different quantities are turned into lot totals and fitted to a least-squares line: total = fixed + per-part × quantity.
The fixed part is treated as per-lot cost such as setup and the slope as per-part machining and material cost, then converted to time.
If the implied per-part time is shorter than pure cutting time, or the fixed part is negative, the price structure cannot be explained by the confirmed conditions alone.
Is a quote below the calculation simply a good deal?
A cheaper quote is not automatically a saving.
A unit price below the per-part cycle cost floor can point to a skipped operation, different cutting data, a different hourly rate or an unrealistic lead time.
Confirm the operation and setup basis behind the gap before ordering to reduce rework and late-delivery risk.
How are VAT-inclusive quotes compared?
Korean value-added tax is 10% under Article 30 of the Value-Added Tax Act.
Choose ‘VAT included’ and each quoted unit price is divided by 1.1 before it is compared with the calculated unit price.
Keep the hourly rate and material cost on the same VAT-excluded basis, otherwise the difference percentages are distorted.
What is missing from the required working days?
Required working days are the lot total time divided by operating hours per day × machines, rounded up.
Material procurement, heat treatment or plating, external measurement, shipping and queueing behind other jobs are not included.
Confirm machine allocation and downstream schedules with the shop to set the real delivery date.
Sources and next steps
Sources were checked on 2026-10-24.
The cutting formulas follow the Sandvik Coromant milling formulas, turning formulas and drilling formulas technical pages.
Article 30 of the Value-Added Tax Act and Articles 3 and 4 of the Subcontracting Act were checked as current text through the Korean National Law Information open API.
Re-enter cutting data, path lengths and hourly rates from the shop for every quote.
Enter the quotes you received in the calculator above and save the TXT worksheet to confirm toolpath and setup basis with the shop.
Once the gaps are resolved you can fix the lot quantity and lead time and place the order.
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