Drill Bits Sizes Chart: ANSI & ISO Metric Standards Easy Explained
Whether you’re working in construction, manufacturing, or DIY projects, understanding drill bit sizes chart is essential to ensure accuracy and efficiency. When it comes to drilling precision holes, choosing the right drill bit size is critical. . In this guide, we’ll explore the two most common drill bit size standards—ANSI (American National Standards Institute) and ISO Metric (International Organization for Standardization). With easy-to-read charts and practical tips, this article is your go-to resource for everything about drill bit sizes.
Why Are Drill Bit Size Charts Important?
Drill bits come in various sizes, each designed for specific materials, hole diameters, and applications. Using the wrong drill bit size can lead to inaccurate holes, tool damage, or compromised project quality. By referencing a drill bits sizes chart, you can select the correct drill bit for the task, reducing errors and improving efficiency.
Types of Drill Bit Standards
There are two widely recognized standards for drill bit sizes:
- ANSI Drill Bit Sizes: Commonly used in the United States, this standard measures drill bit diameters in fractions, numbers, and letters.
- ISO Metric Drill Bit Sizes: Used internationally, this system measures drill bit sizes in millimeters, making it ideal for metric-based projects.
ANSI Drill Bit Sizes Chart
The ANSI standard organizes drill bit sizes into three categories: fractional, letter, and numbered sizes. Here’s a comprehensive chart for easy reference:
Fractional Drill Bit Sizes (ANSI)
Fractional Drill Bit Sizes (ANSI)
| Fractional Size (Inches) | Decimal Equivalent (Inches) | Closest Metric Equivalent (mm) |
|---|---|---|
| 1/64 | 0.0156 | 0.396 |
| 1/32 | 0.0313 | 0.793 |
| 3/64 | 0.0469 | 1.191 |
| 1/16 | 0.0625 | 1.588 |
| 5/64 | 0.0781 | 1.984 |
| 3/32 | 0.0938 | 2.381 |
| 7/64 | 0.1094 | 2.778 |
| 1/8 | 0.125 | 3.175 |
| 9/64 | 0.1406 | 3.572 |
| 5/32 | 0.1563 | 3.969 |
| 11/64 | 0.1719 | 4.366 |
| 3/16 | 0.1875 | 4.763 |
| 13/64 | 0.2031 | 5.159 |
| 7/32 | 0.2188 | 5.556 |
| 15/64 | 0.2344 | 5.953 |
| 1/4 | 0.25 | 6.35 |
| 17/64 | 0.2656 | 6.747 |
| 9/32 | 0.2813 | 7.144 |
| 19/64 | 0.2969 | 7.541 |
| 5/16 | 0.3125 | 7.938 |
| 21/64 | 0.3281 | 8.334 |
| 11/32 | 0.3438 | 8.731 |
| 23/64 | 0.3594 | 9.128 |
| 3/8 | 0.375 | 9.525 |
| 25/64 | 0.3906 | 9.922 |
| 13/32 | 0.4063 | 10.319 |
| 27/64 | 0.4219 | 10.716 |
| 7/16 | 0.4375 | 11.113 |
| 29/64 | 0.4531 | 11.509 |
| 15/32 | 0.4688 | 11.906 |
| 1/2 | 0.5 | 12.7 |
Letter Drill Bit Sizes (ANSI)
| Letter Size | Decimal Equivalent (Inches) | Closest Metric Equivalent (mm) |
|---|---|---|
| A | 0.234 | 5.94 |
| B | 0.238 | 6.05 |
| C | 0.242 | 6.15 |
| D | 0.246 | 6.25 |
| E | 0.25 | 6.35 |
| F | 0.257 | 6.53 |
| G | 0.261 | 6.63 |
| H | 0.266 | 6.76 |
| I | 0.272 | 6.91 |
| J | 0.277 | 7.04 |
Numbered Drill Bit Sizes (ANSI)
| Number Size | Decimal Equivalent (Inches) | Closest Metric Equivalent (mm) |
|---|---|---|
| 1 | 0.228 | 5.79 |
| 2 | 0.221 | 5.62 |
| 3 | 0.213 | 5.41 |
| 4 | 0.209 | 5.31 |
| 5 | 0.205 | 5.21 |
| 6 | 0.204 | 5.18 |
| 7 | 0.201 | 5.11 |
| 8 | 0.199 | 5.05 |
| 9 | 0.196 | 4.98 |
| 10 | 0.193 | 4.90 |
ISO Metric Drill Bit Sizes Chart
The ISO metric system is widely used for projects requiring precise measurements in millimeters. Here’s the complete ISO metric drill bit sizes chart:
| Metric Size (mm) | Closest Fractional Size (Inches) | Decimal Equivalent (Inches) |
|---|---|---|
| 0.5 | – | 0.0197 |
| 0.6 | – | 0.0236 |
| 0.7 | – | 0.0276 |
| 0.8 | – | 0.0315 |
| 0.9 | – | 0.0354 |
| 1.0 | 1/32 | 0.0394 |
| 1.1 | – | 0.0433 |
| 1.2 | – | 0.0472 |
| 1.3 | – | 0.0512 |
| 1.4 | – | 0.0551 |
| 1.5 | 1/16 | 0.0591 |
| 1.6 | – | 0.0630 |
| 1.8 | – | 0.0709 |
| 2.0 | – | 0.0787 |
| 2.2 | – | 0.0866 |
| 2.5 | – | 0.0984 |
| 2.8 | – | 0.1102 |
| 3.0 | 1/8 | 0.1181 |
| 3.2 | – | 0.1259 |
| 3.5 | – | 0.1378 |
| 4.0 | 5/32 | 0.1575 |
| 4.5 | – | 0.1772 |
| 5.0 | 3/16 | 0.1969 |
| 5.5 | – | 0.2165 |
| 6.0 | 1/4 | 0.2362 |
| 6.5 | – | 0.2559 |
| 7.0 | 5/16 | 0.2756 |
| 8.0 | 3/8 | 0.3149 |
| 9.0 | 11/32 | 0.3543 |
| 10.0 | 13/32 | 0.3937 |
Practical Tips for Choosing the Right Drill Bit Size
- Understand Your Material: Choose drill bits suited for the material you’re working with (e.g., wood, metal, or plastic).
- Match the Fastener: For screws, ensure the drill bit matches the diameter of the screw shank.
- Refer to Manufacturer Guidelines: Always check for specific size recommendations in your tools’ manuals.
- Test First: If in doubt, start with a smaller drill bit and increase the size gradually.
Conclusion
Using the correct drill bit size is crucial for achieving precision and durability in your projects. With this guide to ANSI drill bit sizes chart and ISO metric drill bit sizes chart, you’re well-equipped to handle any task, whether it’s a DIY project or a professional job. Bookmark this page for future reference, and don’t hesitate to share it with others in your network.
Drill Bits Sizes Chart FAQ
What size is a drill bit?
Drill bit sizes vary and are categorized into three main systems: fractional sizes (in inches), numbered sizes (#1–#80), and metric sizes (in millimeters). The size of a drill bit refers to its diameter, which determines the size of the hole it will drill. For example, a 1/4-inch drill bit has a diameter of 0.25 inches, while a 6mm drill bit has a diameter of 6 millimeters.
How to calculate drill bit size?
To calculate the drill bit size needed for a specific task:
Determine the hole size required – Identify the size of the screw, bolt, or dowel you will use.
Use the material guidelines – Different materials (wood, metal, plastic) may require slightly different drill bit sizes.
Match to the drill bit size chart – Refer to a drill bits sizes chart (ANSI or ISO) to find the closest size. For tapping threads, the drill size is generally smaller than the bolt size to accommodate threading.
Example: For a 5mm bolt, you may need a 4.2mm drill bit for proper threading.
What size is a 1mm drill bit?
A 1mm drill bit has a diameter of 1 millimeter, which is approximately 0.0394 inches in decimal equivalent. It’s a small-sized drill bit often used for precision tasks like jewelry making, electronics, or delicate repairs.
What size is a 2mm drill bit?
A 2mm drill bit has a diameter of 2 millimeters, which is approximately 0.0787 inches in decimal equivalent. This size is commonly used for light-duty tasks, such as drilling small holes in soft materials like plastic, thin wood, or metal sheets.
Resources: Wikipedia
