👤 By Why Calculator Team ✔ Reviewed by Matt Le (Founder of Why Calculator) 📅 Last Updated April 14, 2026
Drill SFM Calculator
| Drill Diameter | RPM | SFM |
|---|---|---|
| – | – | – |
Disclaimer: While we strive to ensure the accuracy of our calculator tools, we cannot be held responsible for any damages or financial losses resulting from their use.
This Drill SFM Calculator is designed to help machinists and DIY enthusiasts determine the surface feet per minute (SFM) of a drill bit. By inputting the drill bit diameter and RPM, you can quickly calculate the cutting speed to ensure optimal performance. You can select different measurement units for convenience and it displays results in a dynamic table.
This calculator makes it easy to find the right cutting speed for either a professional machining project or a home workshop task.
What is Drill SFM?
Drill SFM (Surface Feet per Minute) is the speed at which the cutting edge of a drill bit moves across the surface of the material being drilled. It is a crucial parameter in machining as it helps determine the appropriate cutting speed for different materials and drill bit types.
It ensures efficiency, accuracy, and tool longevity.
The SFM value depends on the drill bit diameter and the spindle speed (RPM). Using an incorrect SFM can result in overheating or inefficient cutting performance.
How to Calculate Drill SFM?
The formula to calculate Drill SFM is:
SFM = π × D × RPM / 12
where:
- SFM = Surface Feet per Minute
- π (pi) = 3.1416 (constant)
- D = Drill bit diameter (in inches)
- RPM = Revolutions Per Minute (drill speed)
- 12 = Conversion factor to get the value in feet per minute
If the drill diameter is not in inches, convert it before applying the formula.
Example 1: Given a ½ inch drill bit running at 1200 RPM
SFM = (3.1416 × 0.5 × 1200) / 12
SFM = 1884.96 / = 157.08 feet per minute
Answer: The drill bit is cutting at 157.08 feet per minute.
Example 2: Given a 10 mm drill bit running at 1500 RPM
First, convert 10 mm to inches:
10 mm = 10/25.4 = 0.3937 inches
Now, apply the formula:
SFM = (3.1416 × 0.3937 × 1500) / 12
Answer: The drill bit is cutting at 154.69 feet per minute.
Why is SFM Important?
- Prevents Overheating: Using the right surface feet per minute (SFM) keeps the drill bit from overheating. This prevents damage to the tool and helps create better-quality holes.
- Improves Tool Life: A proper cutting speed helps extend the lifespan of the drill bit.
- Enhances Efficiency: Correct SFM ensures optimal material removal rates and reduces machining time.
Related Calculator: