Metric Bolt vs Imperial
Table of Content
- What is Imperial Bolts ?
- What is Metric Bolts ?
- What is the Difference Between Metric and Imperial Bolts ?
- Metric vs. Standard Bolts
- Metric Screws Size Conversion Chart
- Metric and Imperial Bolt Conversion Table
- Equivalents of Metric vs Imperial Bolts
- Advantages of Metric Fasteners Over Imperial
- Metric vs Standard chart
- Difference Between Imperial Thread and Metric Thread
- What is Thread Pitch and Thread Count of Bolt ?
- Thread Pitch is Used in Metric Fasteners
- Threads Per Inch Are Used in British and American Fasteners
- Bolt Size Metric to Imperial
- What is an M10 Bolt in Imperial ?
- Do Cars Use Metric or Imperial Bolts ?
- Can Imperial and Metric Bolts Be Used Interchangeably ?
- Can You Ever Mix Metric and Imperial Nuts and Bolts ?
- Unit Weight of Metric Bolt vs Imperial Bolt
Complete Guide of What is Metric & Imperial Bolt
- ➤ Imperial bolts: Measured in inches.
- ➤ Thread types: UNC, UNF, UNEF.
- ➤ Used in: U.S. and Imperial-based industries.
- ➤ Metric bolts: Measured in millimeters.
- ➤ Thread types: M (coarse, fine).
- ➤ Used in: Metric-based countries.
Check the Differences Between Metric and Imperial Bolts
| Aspect | Metric | Imperial |
|---|---|---|
| Measurement | Millimeters, Pitch | Inches, Threads per Inch |
| Tensile Strength | MPa (Megapascals) | PSI or KSI |
| Markings | Strength Grade (e.g., 8.8) | SAE Grades (e.g., Grade 5) |
| Size | M6, M8, M10, M12, etc. | 1/4", 1/2", 3/4", etc. |
| Standard | ISO Standard | Unified Thread Standard |
| Use | Europe, Asia, Global | U.S. and Canada |
| Aspect | Standard Bolts | Metric Bolts |
|---|---|---|
| Measurement System | Imperial (Inches) | Metric (Millimetres) |
| Thread Pitch | Threads Per Inch (TPI) | Pitch (mm) |
| Head Size | Inches or Fractions of Inches | Millimetres |
| Usage | U.S. Based | International (Europe, Asia) |
| Markings | None | "M" or "ISO M", Strength Grade |
Know More About Metric Screws Conversion Chart & Equivalents of Metric vs Imperial Bolt
| METRIC SCREWS | IMPERIAL SCREWS | ||
|---|---|---|---|
| LENGTH (MM) | DIA (MM) | LENGTH (IN) | NOMINAL SIZE (GAUGE) |
| 30 | 5 | 1 1/4 | 10 |
| 100 | 6 | 4 | 12 |
| 12 | 3 | 1/2 | 4 |
| 80 | 5 | 3 | 10 |
| 40 | 4 | 1 1/2 | 8 |
| 20 | 3 | 3/4 | 4 |
| 70 | 5 | 2 3/4 | 10 |
| 25 | 3 | 1 | 4 |
| 60 | 6 | 2 1/2 | 12 |
| 12 | 3.5 | 1/2 | 6 |
| 90 | 6 | 3 1/2 | 12 |
| 60 | 5 | 2 1/2 | 10 |
| 16 | 3.5 | 5/8 | 6 |
| 50 | 6 | 2 | 12 |
| 60 | 4 | 2 1/2 | 8 |
| 20 | 3.5 | 3/4 | 6 |
| 50 | 5 | 2 | 10 |
| 70 | 4 | 2 3/4 | 8 |
| 25 | 3.5 | 1 | 6 |
| 40 | 5 | 1 1/2 | 10 |
| 30 | 3.5 | 1 1/4 | 6 |
| 20 | 4 | 3/4 | 8 |
| 70 | 6 | 2 3/4 | 12 |
| 25 | 4 | 1 | 8 |
| 100 | 5 | 4 | 10 |
| 30 | 4 | 1 1/4 | 8 |
| 80 | 6 | 3 | 12 |
| 45 | 4 | 1 3/4 | 8 |
| 90 | 5 | 3 1/2 | 10 |
| 50 | 4 | 2 | 8 |
| METRIC (MM) | INCHES (IN) | METRIC (MM) | INCHES (IN) |
|---|---|---|---|
| 15.0813 | 19/32 | 4.7625 | 3/16 |
| 14.2875 | 9/16 | 3.9688 | 5/32 |
| 22.2250 | 7/8 | 8.3344 | 21/64 |
| 9.9219 | 25/64 | 0.3969 | 1/64 |
| 15.8750 | 5/8 | 5.1594 | 13/64 |
| 10.3188 | 13/32 | 0.7938 | 1/32 |
| 25.4000 | 1 | 9.5250 | 3/8 |
| 14.6844 | 37/64 | 4.3656 | 11/64 |
| 11.1125 | 7/16 | 1.5875 | 1/16 |
| 19.8438 | 25/32 | 7.9375 | 5/16 |
| 11.9063 | 15/32 | 2.3813 | 3/32 |
| 19.0500 | 3/4 | 6.7469 | 17/64 |
| 11.5094 | 29/64 | 1.9844 | 5/64 |
| 22.6219 | 57/64 | 8.7313 | 11/32 |
| 12.7000 | 1/2 | 2.7781 | 7/64 |
| 19.4469 | 49/64 | 7.1438 | 9/32 |
| 13.0969 | 33/64 | 3.1750 | 1/8 |
| 16.2719 | 41/64 | 5.5563 | 7/32 |
| 13.4938 | 17/32 | 3.5719 | 9/64 |
| METRIC (PITCH IN MM) | BRITISH STANDARD (THREADS PER INCH) | UNIFIED THREAD STANDARD (THREADS PER INCH) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| SIZE | FINE (MM) | COARSE (MM) | SIZE | BA | FINE (BSF) | COARSE (BSW) | Size | FINE (UNF) | COARSE (UNC) | |
| M100 | -- | 6.00 | 4” | -- | 4.5 | 3 | 4” | -- | 4 | -- |
| M9 | 1.00 | 1.25 | -- | -- | -- | -- | -- | -- | -- | -- |
| -- | -- | -- | -- | -- | -- | -- | -- | 160 | -- | #0000 |
| M78 | 2.00 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| -- | -- | -- | -- | -- | -- | -- | -- | 120 | -- | #000 |
| M14 | 1.50 | 2.00 | 9/16" | -- | 16 | 12 | 9/16” | 18 | 12 | -- |
| M38 | 1.50 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| -- | -- | -- | -- | -- | -- | -- | -- | 90 | -- | #00 |
| M1.6 | 0.20 | 0.35 | -- | -- | -- | -- | -- | 80 | -- | #0 |
| M70 | 4.00 | 6.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M2 | 0.25 | 0.40 | -- | -- | -- | -- | -- | 72 | 64 | #1 |
| M17 | 1.50 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| M20 | 1.50 | -- | 3/4" | -- | 12 | 10 | ¾" | 16 | 10 | -- |
| -- | -- | -- | 1/16" | -- | -- | 60 | -- | -- | -- | -- |
| M22 | 1.50 | 2.50 | 7/8” | -- | 11 | 9 | 7/8” | 14 | 9 | -- |
| M2.5 | 0.35 | 0.45 | -- | -- | -- | -- | -- | 56 | 48 | #3 |
| M8 | 1.00 | 1.25 | 5/16" | -- | 22 | 18 | 5/16” | 24 | 18 | -- |
| M24 | 2.00 | 3.00 | 1" | -- | 10 | 8 | 1” | 14 / 12 | 8 | -- |
| M36 | 3.00 | 4.00 | 1 ½" | -- | 8 | 6 | 1 ½" | 12 | 6 | -- |
| M10 | 1.25 | 1.50 | 3/8" | -- | 20 | 16 | 3/8” | 24 | 16 | -- |
| -- | -- | -- | 3/32" | -- | -- | 48 | -- | -- | -- | -- |
| M30 | 2.00 | 3.50 | 1 ¼" | -- | 9 | 7 | 1 ¼" | 12 | 7 | -- |
| M3 | 0.35 | 0.50 | 1/8" | -- | -- | 40 | 1/8” | 44 | 40 | #5 |
| -- | -- | -- | 5 1/2" | -- | -- | 2.625 | -- | -- | -- | -- |
| M32 | 2.00 | 00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M7 | 0.75 | 1.00 | 9/32" | -- | 26 | -- | -- | -- | -- | -- |
| M4.5 | 0.50 | 0.75 | -- | -- | -- | -- | -- | -- | -- | -- |
| M48 | 4.00 | 5.00 | -- | -- | -- | -- | 1 7/8” | -- | 5 | -- |
| M5 | 0.50 | 0.80 | 3/16" | 32 | 32 | 24 | 3/16” | 32 | 24 | #10 |
| M40 | 3.00 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| -- | -- | -- | 3 ¼" | -- | 5 | 3.25 | 3 ¼" | -- | 4 | -- |
| M5.5 | 0.50 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| M28 | 2.00 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| -- | -- | -- | 1/4" | -- | 26 | 20 | 1/4" | 28 | 20 | -- |
| M42 | 4.00 | 4.50 | -- | -- | -- | -- | -- | -- | -- | -- |
| M11 | 1.00 | 1.50 | -- | -- | -- | -- | -- | -- | -- | -- |
| M62 | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| -- | -- | -- | 7/16” | -- | 18 | 14 | 7/16” | 20 | 14 | -- |
| M58 | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| M12 | 1.25 | 1.75 | 1/2" | -- | 16 | 12 | 1/2" | 20 | 13 | -- |
| M65 | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| -- | -- | -- | 3 ¾" | -- | 4.5 | 3 | 3 ¾" | -- | 4 | -- |
| M15 | 1.50 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| M56 | 4.00 | 5.50 | 2 ¼" | -- | 6 | 4 | 2 ¼" | -- | 4.5 | -- |
| M50 | 3.00 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| M16 | 1.50 | 2.00 | 5/8” | -- | 14 | 11 | 5/8” | 18 | 11 | -- |
| -- | -- | -- | 11/16" | -- | 14 | 11 | -- | -- | -- | -- |
| M80 | 4.00 | 6.00 | 3” | -- | 5 | 3.5 | 3” | -- | 4 | -- |
| M18 | 1.50 | 2.50 | -- | -- | -- | -- | -- | -- | -- | -- |
| -- | -- | -- | 4 3/4" | -- | -- | 2.75 | -- | -- | -- | -- |
| M90 | 4.00 | 6.00 | 3 ½" | -- | 4.5 | 3.25 | 3 ½" | -- | 4 | -- |
| M25 | 2.00 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| -- | -- | -- | 5" | -- | -- | 2.75 | -- | -- | -- | -- |
| M68 | 4.00 | 6.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M27 | 2.00 | -- | 1 1/8” | -- | 9 | 7 | 1 1/8” | 12 | 7 | -- |
| -- | -- | -- | 4 1/4" | -- | 4 | 2.875 | -- | -- | -- | -- |
| M72 | 4.00 | 6.00 | 2 3/4" | -- | 6 | 3.5 | 2 3/4" | -- | 4 | -- |
| -- | -- | -- | 5 1/4" | -- | -- | 2.625 | -- | -- | -- | -- |
| M33 | 2.00 | 3.50 | 1 3/8” | -- | 8 | 6 / 7 | 1 3/8” | 12 | 6 | -- |
| M76 | 4.00 | 6.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M35 | 1.50 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| M64 | 4.00 | 6.00 | 2 ½" | -- | 6 | 4 | 2 ½" | -- | 4 | -- |
| M39 | 3.00 | 4.00 | 1 5/8” | -- | 8 | 5 | 1 5/8” | -- | -- | -- |
| -- | -- | -- | 6 | -- | -- | 2.5 | -- | -- | -- | -- |
| M75 | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| M45 | 4.00 | 4.50 | 1 ¾" | -- | 7 | 5 | 1 ¾" | -- | 5 | -- |
| -- | -- | -- | 5 3/4" | -- | -- | 2.5 | -- | -- | -- | -- |
| M52 | 4.00 | 5.00 | 2” | -- | 7 | 4.5 | 2” | -- | 4.5 | -- |
| -- | -- | -- | 4 1/2" | -- | -- | 2.875 | -- | -- | -- | -- |
| M55 | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| M85 | 4.00 | 6.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M60 | 4.00 | 5.50 | -- | -- | -- | -- | -- | -- | -- | -- |
Refer Advantages of Metric Fasteners Over Imperial & Check Metric vs Standard Chart
| INCHES | METRIC SIZE- PITCH, ISO AND IFI REC. | |
|---|---|---|
| (UNF) | (UNC) | |
| 5/16- 24 | 5/16-18 | M8 x 1.25 |
| 1-1/4- 12 | 1-1/2- 6 | M36 x 4 |
| 7/16- 20 | 7/16-14 | M12 x 1.75 |
| 1- 72 | 1- 64 | M2 x 0.4 |
| 5/8- 18 | 5/8- 11 | M18 x 2 |
| 1/2- 20 | 1/2- 13 | M14 x 2 |
| 3- 56 | 3- 48 | M2.5 x 0.45 |
| 8- 36 | 8- 32 | M4 x 0.7 |
| 1-1/8- 12 | 1-1/4- 7 | M30 x 3.5 |
| 3/8- 24 | 3/8-16 | M10 x 1.5 |
| 1-12 | 1- 8 | M24 x 3 |
| 3/4- 16 | 3/4- 10 | M20 x 2.5 |
| 4- 48 | 4- 40 | M3 x 0.5 |
| 10- 32 | 10- 24 | M5 x 0.8 |
| 1/4- 28 | 1/4- 20 | M 6x 1 |
| 6- 40 | 6- 32 | M3.5 x 0.6 |
View Difference Between Imperial Thread and Metric Thread & Check Bolt Size Metric vs Imperial
| Aspect | Imperial Thread | Metric Thread |
|---|---|---|
| Measurement System | Inches, TPI | Millimeters, Pitch |
| Thread Designation | Diameter + TPI (e.g., 1/4"-20) | "M" + Diameter + Pitch (e.g., M6x1.0) |
| Applications | Common in the US, construction | Widely used globally, automotive, machinery |
| Standards | UTS, NPT | ISO Metric Threads |
- ➤ Thread Pitch: Distance between threads.
- ➤ Thread Count: Number of threads per unit length.
- ➤ Thread Pitch: Distance between threads, in millimeters.
- ➤ Metric Fasteners: Marked with "M".
- ➤ Thread Patterns:
- -Coarse Pitch: Larger gap between threads.
- -Fine Pitch: Smaller gap between threads.
- ➤ UNC: Coarse threads, lower TPI.
- ➤ UNF: Fine threads, higher TPI.
- ➤ BSW: Coarse threads.
- ➤ BSF: Fine threads.
- ➤ BA: Threads marked with "BA."
| METRIC BOLT SIZE | APPROXIMATE IMPERIAL EQUIVALENT |
|---|---|
| M10 | 3/8 inch |
| M20 | 3/4 inch |
| M8 | 5/16 inch |
| M12 | 1/2 inch |
| M6 | 1/4 inch |
| M16 | 5/8 inch |
- ➤ M10 Bolt Diameter: 10 Mm = 0.3937 Inches
- ➤ Imperial Equivalent: 3/8 Inch Bolt
- ➤ Thread Pitch (M10): 1.5 mm
- ➤ Thread Pitch (3/8 inch): 16 TPI
- ➤ Modern Cars: Use Metric Bolts Globally.
- ➤ Older American Cars: May Use Imperial Bolts.
- ➤ General Trend: Use in Automotive Industry.
No, Imperial and Metric bolts cannot be used interchangeably
Because of Different threads, Varying angles, Improper fit, Match systems
Thread Incompatibility:
Different thread pitches and sizes
Poor Fit:
Can cause weak connections.
Safety Risk:
May cause failure under load.
| Bolt Size | Approximate Weight Difference | Imperial (inch) | Metric (mm) |
|---|---|---|---|
| M10 / 3/8" | slightly heavier | 3/8 inch | 10 mm |
| M12 / 1/2" | slightly heavier | 1/2 inch | 12 mm |