Fastener Reference Guide (Metric-Imperial Equivalents)
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When it comes to identifying fastener sizes, thread is key. You have to know when you are dealing with metric or imperial fasteners. From there, you can cross-reference from the table below, which contains data diligently compiled from verified sources.
Metric fasteners use thread pitch
Thread pitch is the distance from one thread to the next (adjacent thread). It is expressed in millimetres.
Metric fasteners are typically prefixed by an M, which makes them easily distinguishable from imperial fasteners.
Thread patterns are classified as either coarse (longer) or fine (shorter) pitch.
American and British fasteners use threads per inch
Threads Per Inch (TPI) is the number of threads in an inch.
When dealing with threaded fasteners from North America, you'll refer to them in Unified Thread Standard (UTS) that use:
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Unified National Coarse (UNC) - Coarse threads*, lower TPI values
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United National Fine (UNF) - Fine threads*, higher TPI values
You may also encounter threaded fasteners from the UK that still use the British Standard:
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British Standard Whitworth (BSW) - Coarse threads*
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British Standard Fine (BSF) - Fine threads*
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British Association (BA) - Typically suffixed with BA
*Labeled in fractional inches (eg. 1/8”) based on nominal size
Metric vs Imperial equivalents
Refer to this table when cross-referencing your bolt, nut or screw. Not all metric fasteners have imperial equivalents, and vice versa.
| Metric (Pitch in mm) | Unified Thread Standard (Threads Per Inch) | British Standard (Threads Per Inch) | ||||||||
| Size | Coarse (mm) | Fine (mm) | Size | Coarse (UNC) | Fine (UNF) | Size | Coarse (BSW) | Fine (BSF) | BA | |
| -- | -- | -- | -- | #0000 | -- | 160 | -- | -- | -- | -- |
| -- | -- | -- | -- | #000 | -- | 120 | -- | -- | -- | -- |
| -- | -- | -- | -- | #00 | -- | 90 | -- | -- | -- | -- |
| M1.6 | 0.35 | 0.20 | -- | #0 | -- | 80 | -- | -- | -- | -- |
| M2 | 0.40 | 0.25 | -- | #1 | 64 | 72 | -- | -- | -- | -- |
| -- | -- | -- | -- | -- | -- | -- | 1/16" | 60 | -- | -- |
| -- | -- | -- | -- | #2 | 56 | 64 | 8BA | -- | -- | 59.1 |
| M2.5 | 0.45 | 0.35 | -- | #3 | 48 | 56 | -- | -- | -- | -- |
| -- | -- | -- | -- | -- | -- | -- | 3/32" | 48 | -- | -- |
| -- | -- | -- | -- | #4 | 40 | 48 | 6BA | -- | -- | 47.9 |
| M3 | 0.50 | 0.35 | 1/8” | #5 | 40 | 44 | 1/8" | 40 | -- | -- |
| M3.5 | 0.60 | 0.35 | -- | #6 | 32 | 40 | 4BA | -- | -- | 38.5 |
| -- | -- | -- | -- | -- | -- | -- | 5BA | -- | -- | 43 |
| M4 | 0.70 | 0.50 | -- | #8 | 32 | 36 | 3BA | -- | -- | 34.8 |
| M4.5 | 0.75 | 0.50 | -- | -- | -- | -- | -- | -- | -- | -- |
| -- | -- | -- | -- | -- | -- | -- | 2BA | -- | -- | 31.4 |
| M5 | 0.80 | 0.50 | 3/16” | #10 | 24 | 32 | 3/16" | 24 | 32 | 32 |
| M5.5 | -- | 0.50 | -- | -- | -- | -- | -- | -- | -- | -- |
| -- | -- | -- | -- | #12 | 24 | 28 | 1BA | -- | -- | 28.2 |
| M6 | 1.00 | 0.75 | -- | -- | -- | -- | 0BA | -- | -- | 25.4 |
| -- | -- | -- | 1/4" | -- | 20 | 28 | 1/4" | 20 | 26 | -- |
| M7 | 1.00 | 0.75 | -- | -- | -- | -- | 9/32" | -- | 26 | -- |
| M8 | 1.25 | 1.00 | 5/16” | -- | 18 | 24 | 5/16" | 18 | 22 | -- |
| M9 | 1.25 | 1.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M10 | 1.50 | 1.25 | 3/8” | -- | 16 | 24 | 3/8" | 16 | 20 | -- |
| M11 | 1.50 | 1.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| -- | -- | -- | 7/16” | -- | 14 | 20 | 7/16” | 14 | 18 | -- |
| M12 | 1.75 | 1.25 | 1/2" | -- | 13 | 20 | 1/2" | 12 | 16 | -- |
| M14 | 2.00 | 1.50 | 9/16” | -- | 12 | 18 | 9/16" | 12 | 16 | -- |
| M15 | -- | 1.50 | -- | -- | -- | -- | -- | -- | -- | -- |
| M16 | 2.00 | 1.50 | 5/8” | -- | 11 | 18 | 5/8” | 11 | 14 | -- |
| -- | -- | -- | -- | -- | -- | -- | 11/16" | 11 | 14 | -- |
| M17 | -- | 1.50 | -- | -- | -- | -- | -- | -- | -- | -- |
| M18 | 2.50 | 1.50 | -- | -- | -- | -- | -- | -- | -- | -- |
| M20 | -- | 1.50 | ¾" | -- | 10 | 16 | 3/4" | 10 | 12 | -- |
| M22 | 2.50 | 1.50 | 7/8” | -- | 9 | 14 | 7/8” | 9 | 11 | -- |
| M24 | 3.00 | 2.00 | 1” | -- | 8 | 14 / 12 | 1" | 8 | 10 | -- |
| M25 | -- | 2.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M27 | -- | 2.00 | 1 1/8” | -- | 7 | 12 | 1 1/8” | 7 | 9 | -- |
| M28 | -- | 2.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M30 | 3.50 | 2.00 | 1 ¼" | -- | 7 | 12 | 1 ¼" | 7 | 9 | -- |
| M32 | 00 | 2.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M33 | 3.50 | 2.00 | 1 3/8” | -- | 6 | 12 | 1 3/8” | 6 / 7 | 8 | -- |
| M35 | -- | 1.50 | -- | -- | -- | -- | -- | -- | -- | -- |
| M36 | 4.00 | 3.00 | 1 ½" | -- | 6 | 12 | 1 ½" | 6 | 8 | -- |
| M38 | -- | 1.50 | -- | -- | -- | -- | -- | -- | -- | -- |
| M39 | 4.00 | 3.00 | 1 5/8” | -- | -- | -- | 1 5/8” | 5 | 8 | -- |
| M40 | -- | 3.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M42 | 4.50 | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M45 | 4.50 | 4.00 | 1 ¾" | -- | 5 | -- | 1 ¾" | 5 | 7 | -- |
| M48 | 5.00 | 4.00 | 1 7/8” | -- | 5 | -- | -- | -- | -- | -- |
| M50 | -- | 3.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M52 | 5.00 | 4.00 | 2” | -- | 4.5 | -- | 2” | 4.5 | 7 | -- |
| M55 | -- | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M56 | 5.50 | 4.00 | 2 ¼" | -- | 4.5 | -- | 2 ¼" | 4 | 6 | -- |
| M58 | -- | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M60 | 5.50 | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M62 | -- | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M64 | 6.00 | 4.00 | 2 ½" | -- | 4 | -- | 2 ½" | 4 | 6 | -- |
| M65 | -- | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M68 | 6.00 | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M70 | 6.00 | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M72 | 6.00 | 4.00 | 2 3/4" | -- | 4 | -- | 2 3/4" | 3.5 | 6 | -- |
| M75 | -- | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M76 | 6.00 | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M78 | -- | 2.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M80 | 6.00 | 4.00 | 3” | -- | 4 | -- | 3” | 3.5 | 5 | -- |
| -- | -- | -- | 3 ¼" | -- | 4 | -- | 3 ¼" | 3.25 | 5 | -- |
| M85 | 6.00 | 4.00 | -- | -- | -- | -- | -- | -- | -- | -- |
| M90 | 6.00 | 4.00 | 3 ½" | -- | 4 | -- | 3 ½" | 3.25 | 4.5 | -- |
| -- | -- | -- | 3 ¾" | -- | 4 | -- | 3 ¾" | 3 | 4.5 | -- |
| M100 | 6.00 | -- | 4” | -- | 4 | -- | 4” | 3 | 4.5 | -- |
| -- | -- | -- | -- | -- | -- | -- | 4 1/4" | 2.875 | 4 | -- |
| -- | -- | -- | -- | -- | -- | -- | 4 1/2" | 2.875 | -- | -- |
| -- | -- | -- | -- | -- | -- | -- | 4 3/4" | 2.75 | -- | -- |
| -- | -- | -- | -- | -- | -- | -- | 5" | 2.75 | -- | -- |
| -- | -- | -- | -- | -- | -- | -- | 5 1/4" | 2.625 | -- | -- |
| -- | -- | -- | -- | -- | -- | -- | 5 1/2" | 2.625 | -- | -- |
| -- | -- | -- | -- | -- | -- | -- | 5 3/4" | 2.5 | -- | -- |
| -- | -- | -- | -- | -- | -- | -- | 6 | 2.5 | -- | -- |
Table values compiled from:
Aside from the thread pitch (metric) or count (imperial), other factors to consider when buying fasteners include:
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Type (bolt, nut or screw)
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Head
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Strength (classified by grade/class)
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Material and finish (coating)
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Tensile properties (low/high tensile)
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Thread length (full/partial)
(We’ll cover them in detail in future articles.)
It’s always great to have a sample of the fastener you’re shopping for, but that won’t always be the case. We have a wide range of fastener listings with pictures that you can use for reference.
If in doubt, reach out to us via chat or email and we’ll assist you promptly.
AIMS’ Note on Buying Industrial Supplies
- Breadth and depth of brands and categories: Go with a supplier that offers a wide range of reputable brands across multiple categories and sub-categories.
- Bulk purchase discounts: For large orders, check if you can take advantage of volume leverage. Some suppliers offer business accounts* that give you access to special pricing (volume discounts), preferential support and even credit eligibility (subject to supplier approval, terms and conditions).
- Product and service information: Evaluate the completeness and usefulness of data in their online product listings. Prudent suppliers will include as much useful information as possible to help you assess and compare products. In terms of service info, the supplier’s FAQs (if any) will give you a good idea of their standard policies*, processes and commitments.
- Promotions: Check for ongoing promotional campaigns so you can get the best prices. Many suppliers run regular discount-based promos. Some can point you to government-hosted rebate programmes like the SafeWork NSW $1000 Small Business Rebate.
- Safety compliance: Make sure the product in question meets Australian safety standards and regulations, especially if there are relevant compliance requirements or work health and safety (WHS) laws that apply to your business or state. Look for relevant certifications and markings where necessary.
- Supplier reliability: Choose reputable suppliers with a proven track record of delivering quality products and reliable customer service.
- Warranty and support: Check warranty terms and after-sales support* options, as this can be crucial in case of product defects or performance issues.
- Lead time and availability: Confirm product availability and estimated delivery times to avoid delays in your projects.
- Returns: Familiarise yourself with the suppliers returns and exchange policy in case you receive incorrect or damaged items.
- Delivery: Clarify delivery terms, including estimated delivery times, shipping costs and who handles insurance during transit (where applicable).
*Need help with a purchase decision? Contact us directly via chat or send an email to sales@aimsindustrial.com.au.
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