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.
or: RPM = (SMM × 318.3) ÷ Tool Diameter
mm/min = RPM × Flutes × Chip Load (mm)
+ (Labor Rate × Cycle Time) + Setup + Tooling
÷ (Monthly Revenue Gain − Monthly Costs)
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.
■ Fast rank (KD 0–10) ■ Good (KD 11–20) ■ Medium (KD 21–30)
The foundation of every CNC job. Enter tool diameter, flute count, material, and chip load — get optimal RPM and feed rate in IPM or mm·min instantly. Covers carbide and HSS end mills, drills, routers, and turning inserts across 50+ materials from aluminum 6061 to 316 stainless to titanium Ti-6Al-4V. Includes chip load recommendations by material and tool type, plus a troubleshooting guide for dust, chatter, and burning.
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 |
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."
CNC Tools & Tooling These Calculators Help You Use Right
Once you have your feeds, speeds, and cost numbers, here are the tooling and equipment categories the calculators are designed around — pre-filtered for professional and job-shop grades on Amazon.
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