Free CNC Calculators

Spec the machine, then sanity-check the economics. Feed rate & RPM, machining cost per part, machine ROI, and cost-per-part (machine + labor split) — all in one place. 100% free, no signup.

4 Free Tools Metric & Imperial Mills, Routers & Lathes No Signup Required

Free Calculators

IPM

Imperial + mm·min Metric

50+

Materials in Feed Rate Tool

Signup Required

⚙ Core CNC Formulas — Used in These Calculators

Spindle Speed (RPM)

RPM = (SFM × 3.82) ÷ Tool Diameter
or: RPM = (SMM × 318.3) ÷ Tool Diameter

Feed Rate

IPM = RPM × Flutes × Chip Load
mm/min = RPM × Flutes × Chip Load (mm)

Cost per Part

Cost = (Machine Rate × Cycle Time)
+ (Labor Rate × Cycle Time) + Setup + Tooling

Payback Period

Payback = Machine Cost
÷ (Monthly Revenue Gain − Monthly Costs)

🔍 Quick-Win Keywords — CNC Hub

These CNC-specific queries have KD 5–20 with strong commercial intent from machinists and job shop owners. The top-ranking pages are mostly tooling brand calculators (Kennametal, Sandvik) and dedicated machining sites — none match TWC's free, unbranded, metric + imperial format. "People Also Ask" boxes for these queries are largely unanswered by free tools.

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How to Use These CNC Calculators

Every CNC job has two distinct phases: technical setup (feeds, speeds, chip load) and business economics (cost per part, margin, machine ROI). Most machinists are good at one and weak at the other. These four tools cover both — in the exact sequence you need them.

1 Dial In Feeds & Speeds

Start with the Feed Rate Calculator before touching the machine. Enter your material, tool diameter, flute count, and target chip load — get starting RPM and IPM. Always run a test pass and adjust one variable at a time: if you see dust, raise feed or lower RPM; chatter means reduce depth or adjust RPM; burning means check chip evacuation first.

2 Measure Actual Cycle Time

Run your test part and measure the actual cycle time with a stopwatch — not the CAM estimate. CAM programs consistently underestimate cycle time by 15–30% on complex parts. The actual measured cycle time is the only accurate input for cost calculations. Use it in Step 3.

3 Calculate Cost per Part

Run the Cost per Part Calculator with measured cycle time, your machine rate, and burdened operator rate. This gives you the direct cost floor — the minimum you can charge and break even on direct costs alone, before overhead and profit.

4 Build the Full Quote

Take the cost-per-part from Step 3 into the CNC Machining Cost Calculator to add setup amortization, material cost, tooling, and your overhead percentage. Output a complete cost breakdown and a quote price at your target gross margin. Never quote from memory.

Quick SFM Reference — Common CNC Materials

Starting surface feet per minute (SFM) values for carbide end mills with flood coolant. Increase 10–20% for coated tooling. Decrease 30% for HSS. Use the Feed Rate Calculator to convert SFM → RPM for your tool diameter.

Material	SFM (carbide)	SMM (carbide)	Chip Load 1/4" 4-fl	Notes
Aluminum 6061-T6	800–1,000	244–305	0.003–0.005"	Most common, cuts fast
Aluminum 7075-T6	700–900	213–274	0.003–0.004"	Harder, slightly lower SFM
Mild Steel 1018	300–500	91–152	0.001–0.002"	Use flood coolant
Tool Steel (D2, H13)	150–250	46–76	0.0008–0.0015"	Low SFM, high rigidity needed
304 Stainless Steel	100–200	30–61	0.001–0.002"	Work hardens — keep chip load up
Titanium Ti-6Al-4V	100–150	30–46	0.001–0.0015"	High pressure coolant essential
Brass C360	500–700	152–213	0.002–0.004"	Free-machining, sharp tools
Delrin / Acetal	600–900	183–274	0.003–0.006"	Air blast, no coolant needed
MDF / Plywood (router)	400–600	122–183	0.006–0.010"	Large chip load to clear dust

💡 The #1 CNC Quoting Mistake — Charging Machine Time at Labor Rate

A $28/hr machinist running a $120/hr VMC is NOT a $28/hr operation. The machine rate should be charged separately from the operator labor rate — and when one operator runs two machines simultaneously, the labor cost per machine drops to $14/hr while the machine rate stays at $120/hr each. The Cost per Part Calculator handles this split automatically. Shops that don't separate these costs consistently underprice their machining and wonder why they can't profit despite being "busy."

Using calculator results responsibly

Turn the result into a verified shop decision

1. Check the inputs

Use measured dimensions, current labor and machine rates, and the correct material or process assumptions.

2. Compare with machine limits

Confirm the result against the machine manual, tooling data, applicable code requirements and available capacity.

3. Validate before production

Run a controlled test, record the actual outcome and revise the planning value when shop evidence differs.

Frequently Asked Questions

Two formulas: RPM = (SFM × 3.82) ÷ Tool Diameter (imperial) or RPM = (SMM × 318.3) ÷ Tool Diameter (metric). Then Feed Rate (IPM) = RPM × Number of Flutes × Chip Load per Tooth. Example: 1/2" 4-flute carbide end mill in aluminum 6061 at 900 SFM: RPM = (900 × 3.82) ÷ 0.5 = 6,876 RPM. At 0.004" chip load: IPM = 6,876 × 4 × 0.004 = 110 IPM. These are starting values — always run a test pass and verify with chip color and sound before locking in for production. Use the CNC Feed Rate Calculator to handle the math for any material and tool combination.

CNC machining cost per part = Direct material + (Machine rate × Cycle time) + (Operator burdened rate × Cycle time ÷ machines per operator) + (Setup time × Labor rate ÷ Batch size) + Tooling cost per part. For a 5-minute cycle on a $95/hr VMC with a $38/hr burdened operator running 1 machine, 30-min setup on 20 parts, $3 tooling: ($95 × 5/60) + ($38 × 5/60) + ($38 × 0.5 ÷ 20) + $3 = $7.92 + $3.17 + $0.95 + $3.00 = $15.04 direct cost per part (before material and overhead). Use the CNC Machining Cost Calculator to build this breakdown for your actual numbers.

For carbide end mills in aluminum 6061-T6: 0.002–0.004" per tooth for 1/4" tools, 0.003–0.005" for 3/8", and 0.004–0.006" for 1/2". These are conservative starting values — high-performance coated tools can run 0.006–0.008" chip load in aluminum with adequate chip evacuation. The key diagnostic: if you're making fine powder/dust instead of actual chips, your chip load is too low — raise feed rate or lower RPM. Built-up edge (BUE) on the flutes means your SFM is too low — increase spindle speed. The Feed Rate Calculator includes material-specific chip load recommendations and a troubleshooting guide.

Simple payback = Machine cost ÷ Monthly net benefit. Monthly net benefit = (Additional revenue the machine enables) − (Machine payment + operating costs). For a $120,000 VMC at $2,800/month financed, generating $8,500/month in new machining revenue at 60% gross margin: monthly gross profit = $5,100, less machine payment $2,800 = $2,300/month net. Payback on down payment ($24,000) = $24,000 ÷ $2,300 = 10.4 months. The CNC Machine ROI Calculator also factors in utilization rate, labor savings, and maintenance to produce a 5-year cost-of-ownership comparison for the business case.

Machine rate = the cost to run the machine for one hour: depreciation + maintenance + tooling amortization + electricity + floor space allocation. A typical VMC runs $80–$150/hr machine rate. Operator labor rate = the burdened cost of the person running the machine: base wage + payroll taxes + benefits + workers' comp. When one operator runs two machines simultaneously, the labor cost per machine is halved ($19/hr burdened on 2 machines = $9.50/machine) while the machine rate stays constant at $120/hr each. Confusing these two — or charging everything at a single blended rate — is the most common quoting error in job shops. The Cost per Part Calculator keeps them separate so your quotes stay accurate.

Yes. The CNC Feed Rate Calculator covers CNC routers for wood, MDF, plywood, acrylic, HDPE, and other sheet goods, not just metal-cutting mills. Key differences for routers: chip load is typically larger (0.006–0.012" in wood to clear dust), and the feed rate is often clamped by the machine's maximum axis speed rather than spindle power. For most hobbyist-to-commercial routers (ShopBot, Avid, Laguna), maximum feed rates of 150–300 IPM are the practical limit regardless of what the chip load formula calculates. The tool also includes MDF and plywood in the material library with appropriate SFM ranges for spiral upcut and compression bits.

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