Material Removal Rate Calculator
Work out the material removal rate for a machining cut. Pick the process (milling, turning or drilling), enter the cutting parameters, and get the removal rate in cubic inches per minute (plus cm³/min and in³/hour) with the spindle and motor power needed for your material — with by-parameter and by-material tables and a downloadable PDF.
| Depth | Removal rate | Spindle hp | Motor hp |
|---|---|---|---|
| Enter parameters to compare | |||
| Material | Unit power | Spindle hp | Motor hp |
|---|---|---|---|
| Enter parameters to compare | |||
How to use the MRR calculator
Four quick steps turn a machining cut into its material removal rate — in³/min, cm³/min and in³/hour — plus the spindle and motor power your material needs, with by-parameter and by-material tables and a downloadable report.
Pick the process
Milling, turning, or drilling — the inputs relabel to match.
Enter the parameters
Depth, width and feed for milling; speed and feed for turning; diameter and feed for drilling.
Set material & efficiency
Choose the workpiece material (unit power) and your spindle drive efficiency.
Read results & save a PDF
Get the removal rate, spindle and motor power in hp and kW — then download a report.
The formulas behind the removal rate
Each process has its own MRR formula. The calculator computes the rate in cubic inches per minute, converts the units, then estimates spindle and motor power from the material’s unit power.
▶ Worked example
A milling cut 0.1 in deep × 0.5 in wide at a 20 in/min table feed, in steel, with an 80% efficient drive.
MRR is 0.1 × 0.5 × 20.
= 1.0 in³/min (16.4 cm³/min · 60 in³/hour)
Spindle power is 1.0 × 1.0 = 1.0 hp (steel unit power 1.0), so the motor needs 1.0 ÷ 0.80 = 1.25 hp — about 0.93 kW.
Material removal rate quick reference
The MRR formula for each process, the unit power of common materials, and how rate and power climb as you deepen a milling cut.
| Process | MRR formula | Parameters |
|---|---|---|
| Milling | depth × width × feed rate | DOC, WOC (in), feed (in/min) |
| Turning | 12 × cutting speed × depth × feed | SFM, DOC (in), feed (in/rev) |
| Drilling | (π ÷ 4) × diameter² × feed rate | drill dia (in), feed (in/min) |
Result is in cubic inches per minute, then converted to cm³/min and in³/hour.
| Material | Unit power (hp·min/in³) |
|---|---|
| Aluminum | 0.3 |
| Cast iron | 0.6 |
| Steel | 1.0 |
| Stainless steel | 1.4 |
Representative guide values. The real figure shifts with alloy, hardness, tool, coolant and tool wear.
| Depth of cut | MRR (in³/min) | Spindle hp | Motor hp |
|---|---|---|---|
| 0.05 in | 0.50 | 0.50 | 0.63 |
| 0.10 in | 1.00 | 1.00 | 1.25 |
| 0.15 in | 1.50 | 1.50 | 1.88 |
| 0.20 in | 2.00 | 2.00 | 2.50 |
| 0.30 in | 3.00 | 3.00 | 3.75 |
Width 0.5 in, feed 20 in/min, steel (unit power 1.0), 80% efficiency. Rate and power scale in step with each parameter.
Everything the calculator gives you
One cut produces a full rate-and-power profile, not just a single number.
Material removal rate reference numbers
Built for anyone running metal-cutting
Machinists, shop owners, and students all use MRR to dial in cuts and size machines.
Dialing in a cut and checking it against the spindle on hand. A quick MRR and power read turns a guess into a number before the tool touches metal.
- See the removal rate from your depth, width and feed
- Check the power against the machine’s rating
- Compare milling, turning and drilling cuts
Estimating cycle times, sizing a machine for a job, and quoting work. Removal rate drives how long a part takes and what spindle it needs.
- Turn a removal rate into in³/hour for cycle time
- Size the motor power a job demands
- Hand a customer a clean PDF of the figures
Learning how removal rate and cutting power relate, and how the three processes differ, with every figure worked out in one place.
- See MRR, unit power and motor hp together
- Watch power rise in step with the removal rate
- Compare how materials change the power needed
Get the most from a removal-rate estimate
Small habits make an MRR and power estimate far more useful.
Check power against the spindle
A high MRR is only usable if the motor can drive it. Compare the motor hp with your machine’s rating.
Mind the material
Stainless needs over four times the power of aluminum for the same rate. Pick the right unit power.
Each parameter scales linearly
In milling, doubling depth, width or feed doubles both the rate and the power. Trade them to suit.
Turning uses SFM
Cutting speed is in surface feet per minute, so the formula multiplies by 12 to land in in³/min.
Allow for tool wear
A dull edge needs far more power for the same cut. Size with headroom and watch for rising load.
Respect the tool’s limits
The tool maker’s max depth and feed can be the real ceiling, not the machine’s power.
Balance rate against finish
The fastest cut is rarely the best finish. Rough at high MRR, then slow down for the final pass.
Frequently asked questions
Common questions about material removal rate, cutting power, and unit conversions.
Material removal rate (MRR) is the volume of material a cutting process removes per unit of time, usually in cubic inches per minute. It is a direct measure of how fast a machining job gets done.
A higher MRR means faster cutting and shorter cycle times, but it also demands more spindle power and puts more load on the tool. The rate depends on the process — milling, turning or drilling — and on the cutting parameters you set.
This calculator works out the MRR from your process and parameters, converts it to cm3/min and in3/hour, and estimates the spindle and motor power needed for your material.
For milling, the material removal rate is the depth of cut times the width of cut times the feed rate: MRR = depth x width x feed rate, in cubic inches per minute when the depths are in inches and the feed is in inches per minute.
For example, a cut 0.1 inch deep and 0.5 inch wide at a 20 inch-per-minute table feed removes 0.1 x 0.5 x 20, which is 1.0 cubic inch per minute.
All three factors scale the rate in direct proportion, so doubling the depth, the width or the feed doubles the removal rate — and the power required. This calculator does the milling math and shows the rate and power together.
For turning, the removal rate is 12 times the cutting speed in surface feet per minute, times the depth of cut, times the feed per revolution: MRR = 12 x SFM x depth x feed. The 12 converts feet to inches so the result is in cubic inches per minute.
For drilling, the whole hole cross-section is being cut, so the rate is the hole area times the feed rate: MRR = (pi divided by 4) x diameter squared x feed rate, with the diameter in inches and the feed in inches per minute.
This calculator switches to the right formula when you pick the process and relabels the inputs — cutting speed and feed per revolution for turning, drill diameter and feed rate for drilling.
The spindle power is the removal rate times the material’s unit power (specific cutting energy): power at the spindle = MRR x unit power. Unit power is roughly 0.3 horsepower per cubic inch per minute for aluminum, 0.6 for cast iron, 1.0 for steel and 1.4 for stainless.
The motor has to supply more than the spindle sees, because the drive is not perfectly efficient. Motor power = spindle power divided by efficiency, where efficiency is typically 75 to 90 percent.
For example, removing 1.0 cubic inch of steel per minute needs about 1.0 horsepower at the spindle, or about 1.25 horsepower at the motor at 80 percent efficiency. This calculator reports both, in horsepower and kilowatts.
Unit power — also called specific cutting energy or the power constant Kp — is the power needed to remove one cubic inch of a given material per minute. It captures how hard a material is to cut.
Softer materials have a low unit power, so they cut with little power; harder and tougher materials need much more. Common guide values are about 0.3 horsepower per cubic inch per minute for aluminum, 0.6 for cast iron, 1.0 for steel and 1.4 for stainless steel.
The real value shifts with the exact alloy, its hardness, the tool, the coolant and how worn the edge is. This calculator uses representative figures so you can estimate power and size a machine; confirm against your tooling data for a tight job.
Because milling MRR is depth times width times feed, you can raise it by increasing any of the three — a deeper cut, a wider cut, or a faster feed. For turning, a higher cutting speed, depth or feed does the same; for drilling, a bigger drill or a faster feed.
Each increase removes metal faster but also raises the spindle power, the cutting forces and the heat, so the practical ceiling is set by your machine’s power, the tool’s strength and the finish you need. Strategies like high-feed milling trade a light depth for a very high feed.
This calculator lets you try each change and immediately see the new removal rate and power, with a by-parameter table so you can find the fastest cut your machine can drive.
A machine bogs down or stalls when the cut demands more power than the motor can deliver. Removal rate and power rise together, so pushing the MRR too high on a limited spindle is the usual cause.
Check the motor power the cut needs — removal rate times unit power, divided by efficiency — against your machine’s rated horsepower. If it is over, reduce the depth, width or feed, or switch to a lighter unit-power material or a sharper tool, since a dull tool can need far more power for the same cut.
This calculator estimates the motor horsepower and kilowatts required, so you can compare it with your machine before you start the cut.
One cubic inch equals 16.387 cubic centimeters, so to convert a removal rate from cubic inches per minute to cubic centimeters per minute, multiply by 16.387.
For example, 1.0 cubic inch per minute is about 16.39 cubic centimeters per minute. To get cubic inches per hour instead, multiply the per-minute figure by 60 — so 1.0 in3/min is 60 in3/hour.
This calculator shows the removal rate in cubic inches per minute, cubic centimeters per minute and cubic inches per hour at once, and the power in both horsepower and kilowatts.
Disclaimer: US units (inches, in³/min, hp). Milling: MRR = depth × width × feed rate. Turning: MRR = 12 × cutting speed (SFM) × depth × feed (ipr). Drilling: MRR = (π ÷ 4) × diameter² × feed rate. Power uses an average unit power (specific cutting energy) that varies with the exact alloy, hardness, tool, coolant and tool wear. Use the figures as a guide for feeds, speeds and machine sizing, and stay within the tool maker’s and machine’s rated limits.