Inches Per Minute Converter
A saw that cuts at 60 inches per minute moves 25.4 mm every second, which is exactly 1 inch each second.
Quick answer: Multiply the speed in in/min by 0.423333 to get mm/s. For example, 30 in/min is 12.7 mm/s, 60 in/min is 25.4 mm/s and 100 in/min is 42.333 mm/s.
The inches per minute to mm/s formula
Speed in millimetres per second equals speed in inches per minute times 0.4233333.
The factor 0.423333 is 25.4 divided by 60, since an inch is exactly 25.4 mm and a minute is 60 seconds.
Take 30 in/min. 30 × 0.4233333 gives 12.7 mm/s.
Take 60 in/min. 60 × 0.4233333 gives 25.4 mm/s.
Inches per minute and millimetres per second
Inches per minute is the usual feed rate on milling machines, routers and some printers.
Millimetres per second is a metric speed that matches how a person judges motion by eye.
How to convert inches per minute to mm/s step by step
- Write down the speed in inches per minute.
- Multiply it by 0.4233333.
- Round to the digits you need.
- Write the unit mm/s after the answer.
Example 1: 30 in/min
- Start with 30 in/min.
- 30 × 0.4233333 = 12.7.
- The speed is 12.7 mm/s.
30 in/min = 12.7 mm/s
Example 2: 60 in/min
- Start with 60 in/min.
- 60 × 0.4233333 = 25.4.
- The speed is 25.4 mm/s.
60 in/min = 25.4 mm/s
Example 3: 100 in/min
- Start with 100 in/min.
- 100 × 0.4233333 = 42.333.
- The speed is 42.333 mm/s.
100 in/min = 42.333 mm/s
Round only at the end. Rounding in the middle of a sum adds small errors that grow.
inches per minute to mm/s conversion table
| inches per minute (in/min) | millimetres per second (mm/s) | in/s |
|---|---|---|
| 1 in/min | 0.4233 mm/s | 0.0167 in/s |
| 2 in/min | 0.8467 mm/s | 0.0333 in/s |
| 5 in/min | 2.117 mm/s | 0.0833 in/s |
| 10 in/min | 4.233 mm/s | 0.1667 in/s |
| 20 in/min | 8.467 mm/s | 0.3333 in/s |
| 30 in/min | 12.7 mm/s | 0.5 in/s |
| 40 in/min | 16.933 mm/s | 0.6667 in/s |
| 50 in/min | 21.167 mm/s | 0.8333 in/s |
| 60 in/min | 25.4 mm/s | 1 in/s |
| 80 in/min | 33.867 mm/s | 1.333 in/s |
| 100 in/min | 42.333 mm/s | 1.667 in/s |
| 120 in/min | 50.8 mm/s | 2 in/s |
| 200 in/min | 84.667 mm/s | 3.333 in/s |
The highlighted row is the default of the calculator. The last column gives in/s.
A quick mental shortcut for inches per minute to mm/s
Divide by 2.4 for a fast answer. 120 in/min ÷ 2.4 = 50 mm/s, and the exact answer is 50.8.
Or remember that 60 in/min is 25.4 mm/s and scale from there.
Feed rates in practice
A CNC feed of 30 in/min is 12.7 mm/s. A feed of 100 in/min is 42.33 mm/s.
A slow cut at 5 in/min is 2.12 mm/s.
More values at a glance
0.5 inches per minute is 0.2117 millimetres per second. 2 inches per minute is 0.8467 millimetres per second. 5 inches per minute is 2.1167 millimetres per second.
10 inches per minute is 4.2333 millimetres per second. 25 inches per minute is 10.5833 millimetres per second. 100 inches per minute is 42.3333 millimetres per second.
Each answer is the input times 0.4233. You can use the same factor for any value that is not listed here.
The unit sizes
One of the inches per minute equals 0.4233 millimetres per second. One of the millimetres per second equals 2.3622 inches per minute.
If a result looks very large or very small, compare it with these sizes before you use it.
Checking in reverse
Take 4.2333 millimetres per second and divide by 0.4233. You get back 10 inches per minute. If you do not, one of the numbers was typed or rounded wrongly.
More conversions in a row
0.1 inches per minute is 0.0423 millimetres per second. 0.25 inches per minute is 0.1058 millimetres per second. 1 inches per minute is 0.4233 millimetres per second.
3 inches per minute is 1.27 millimetres per second.
7 inches per minute is 2.9633 millimetres per second. 15 inches per minute is 6.35 millimetres per second. 40 inches per minute is 16.9333 millimetres per second.
60 inches per minute is 25.4 millimetres per second.
75 inches per minute is 31.75 millimetres per second. 150 inches per minute is 63.5 millimetres per second. 200 inches per minute is 84.6667 millimetres per second.
500 inches per minute is 211.6667 millimetres per second.
Rounding the factor
The factor 0.4233 is long. If you cut it to 0.423, 100 inches per minute becomes 42.3 millimetres per second instead of 42.3333.
That is an error of about 0.079 percent, which is fine for a rough check but not for exact work.
Doubling and scaling
The conversion is a straight line through zero. Double the speed in inches per minute and the speed in millimetres per second doubles too.
So 20 inches per minute is 8.4667 millimetres per second, and 40 inches per minute is 16.9333 millimetres per second. You can build any value from the ones in the table.
Quick conversion answers
| Conversion | Result |
|---|---|
| 10 in/min | 4.233 mm/s |
| 20 in/min | 8.467 mm/s |
| 30 in/min | 12.7 mm/s |
| 60 in/min | 25.4 mm/s |
| 100 in/min | 42.333 mm/s |
| 200 in/min | 84.667 mm/s |
Where this conversion is used
Machinists read feed rates in inches per minute and convert them for metric machines.
Designers and hobby users compare printer or router speeds across brands.
Common mistakes to avoid
- Using 25.4 alone. That ignores the 60 seconds in a minute.
- Multiplying by 60. That is for in/s to in/min.
- Dividing instead of multiplying. The mm/s figure is smaller than the in/min figure here.
- Mixing in/min with ipm and ips. Check which unit a spec means.
Related converters
Frequently asked questions
How many millimetres per second is 1 in/min?
1 in/min is 0.4233333 mm/s.
How many millimetres per second is 60 in/min?
60 in/min is 25.4 mm/s.
How many inches per minute is 1 mm/s?
1 mm/s is 2.362205 in/min.
How many mm/s is 60 in/min?
It is exactly 25.4 mm/s.
How many in/s is 60 in/min?
It is exactly 1 in/s.
Is the factor exact?
Yes. It is 25.4 divided by 60, and both numbers are exact.
Sources
- CASRAI: The metre (casrai.org)
