Spanner Size Chart (Metric-Imperial Equivalents)

For your convenience, here is a simplified chart of which spanner you should use for what size of bolt or nut you need to turn, including a cross-reference table of common and alternative metric and imperial (UNC/UNF) values.

Are spanners and wrenches the same?

They essentially have the same purpose: to tighten and loosen nuts and bolts. Nevertheless, they have distinct characteristics designed for specific use cases. 

Put simply: 

  • Spanners have slimmer, fixed-sized heads that are designed to drive nuts and bolts of specific sizes. 
  • Wrenches have a thicker “head" with an adjustable/movable lower “jaw” and are designed to drive nuts and bolts of a range of sizes. Being adjustable, you can virtually use them on any bolt the head and jaw can clamp onto. 

Shop for spanners and wrenches.

 

Metric vs Imperial equivalents

Refer to this table when referencing which spanner size to use for your bolt, nut or screw with a hexagonal head. 

Spanner Size in Metric (mm) Spanner Size in Imperial UNC/UNF
Metric Threads Alternative Sizing Class 4.6/8.8 Structural Stainless SAE Decimal Inches Grade 5/8 AF
    AS 1111 AS 1252 DIN 931 / 933 / 934     AS 2465
M 1.6 --- 3.20 --- 3.20 --- --- ---
M 2.0 --- 4.00 --- 4.00 --- --- ---
M 2.5 --- 5.00 --- 5.00 --- --- ---
M 3.0 --- 5.50 --- 5.50 --- --- ---
--- 3.18 --- --- --- 1/8 0.125 ---
M 4.0 --- 7.00 --- 7.00 5/32 0.156 ---
--- 4.76 --- --- --- 3/16 0.188 ---
M 5.0 --- 8.00 --- 8.00 3/16 0.188 ---
--- 5.56 --- --- --- 7/32 0.218 ---
M 6.0 6.35 10.00 --- 10.00 1/4 0.250 7/16
M 7.0 --- 11.00 --- 11.00 --- 0.267 ---
--- 7.14 --- --- --- 9/32 0.281 ---
M 8.0 --- 13.00 --- 13.00 5/16 0.313 1/2
--- --- --- --- --- 11/32 0.343 ---
M 9.0 9.50 --- --- --- 3/8 0.375 9/16
M 10.0 --- 16.00 --- 17.00 3/8 0.375 9/16
M 11.0 --- --- --- --- 7/16 0.438 5/8
M 12.0 --- 18.00 21.00 19.00 1/2 0.500 3/4
--- 12.70 --- --- --- 1/2 0.500 3/4
M 13.0 --- --- --- --- 1/2 0.500 3/4
M 14.0 14.30 21.00 --- 22.00 9/16 0.563 13/16
M 15.0 --- --- --- --- 9/16 0.563 13/16
M 16.0 --- 24.00 27.00 24.00 5/8 0.625 15/16
M 17.0 --- --- --- --- 21/32 0.656 ---
--- 17.50 --- --- --- 11/16 0.688 ---
M 18.0 --- 27.00 --- 27.00 11/16 0.688 ---
M 19.0 --- --- --- --- 3/4 0.750 1-1/8
M 20.0 --- 30.00 32.00 30.00 3/4 0.750 1-1/8
--- 20.64 --- --- --- 13/16 0.813 ---
M 21.0 --- --- --- --- --- 0.827 ---
M 22.0 --- 34.00 36.00 32.00 7/8 0.875 1-5/16
M 23.0 --- --- --- --- 29/32 0.906 ---
M 24.0 --- 36.00 41.00 36.00 15/16 0.938 1-1/2
M 25.0 --- 36.00 41.00 36.00 1 1.000 1-1/2
M 26.0 --- --- --- --- 1-1/16 1.0625 ---
M 27.0 --- 41.00 46.00 41.00 1-1/8 1.125 1-11/16
M 30.0 --- --- --- --- 1-3/16 1.188 ---
M 31.0 31.75 46.00 50.00 46.00 1-1/4 1.250 1-7/8
M 32.0 --- 46.00 50.00 46.00 1-1/4 1.250 1-7/8
M 33.0 34.00 50.00 --- 50.00 1-3/8 1.375 2-1/16
--- 35.00 --- --- --- 1-3/8 1.375 2-1/16
M 36.0 38.00 55.00 60.00 55.00 1-1/2 1.500 2-1/4
M 39.0 39.69 60.00 --- 60.00 1-9/16 1.562 ---
--- 40.00 --- --- --- 1-9/16 1.562 ---
--- 41.00 --- --- --- 1-5/8 1.625 ---
M 42.0 42.86 65.00 --- 65.00 1-11/16 1.688 ---
M 45.0 --- 70.00 --- 70.00 1-3/4 1.75 2-5/8
M 48.0 --- 75.00 --- 75.00 --- 1.88 ---
M 50.0 --- --- --- --- 2 2.000 ---
M 52.0 --- 80 --- 80 2 2.000 3
M 54.0 --- --- --- --- 2-1/8 2.125 ---
M 56.0 57.00 85 --- 85 2-1/4 2.250 3-3/8
M 60.0 --- 90 --- 90 2-3/8 2.375 ---
--- 63.50 95 --- 95 2-1/2 2.500 3-3/4
M 64.0 --- 95 --- 95 2-1/2 2.500 3-3/4
M 68.0 --- 100 --- 100 --- --- ---
M 72.0 --- 105 --- 105 2-3/4 --- 4-1/8
M 76.0 --- 110 --- 110 --- --- ---
M 80.0 --- 115 --- 115 3 3.000 4-1/2
M 85.0 --- 120 --- 120 --- --- ---
M 90.0 --- 130 --- 130 --- --- ---
M 95.0 --- 135 --- 135 --- --- ---
M 100.0 --- 145 --- 145 --- --- ---
M 105.0 --- 150 --- 150 --- --- ---
M 110.0 --- 155 --- 155 --- --- ---

Table labels:

  • A/F: Across Flats
  • AS: Australian Standard 
  • DIN: Deutsches Institut für Normung (German Standard) 
  • SAE: Society of Automotive Engineers (American Standard originally established for the automotive industry) 
  • AF: Across Flats 
  • UNC: Unified National Coarse  
  • UNF: Unified National Fine 

Notes:

  • Not all metric fasteners have imperial equivalents, and vice versa. 
  • Some metric values are close enough to essentially have the same imperial counterpart. In this case, you can use the same spanner size on them.

Important:

  • Always consult a detailed spanner size chart for apprpriate tool selection.

You may want to consider getting the Engineers Black Book (3rd Edition – Metric) for more complete information, specifically:

  • Metric (millimetres) and UNF/UNC values for thread sizes
  • Metric (millimetres) and UNF/UNC values for spanner sizes (A/Fs)
  • Metric (millimetres) and UNF/UNC values spanner minimum and maximum openings
  • Metric (millimetres) and imperial (inches) in BS (Whitworth) values and nearest fitting spanner sizes

 

More size charts

  • Anchor Bolt Size Chart: Sort through a wide variety of metric anchor bolt types: countersunk head sleeve anchor, drop-in anchor, hex flange nut sleeve anchor, flush head sleeve anchor and stud anchor. Common metric diameters listed.
  • Drill Bit Size Chart: Choose the right bit size to ensure a proper fit for your intended gauge sizing. Metric (SI) and imperial (US decimal / fractional inches) values matched.
  • Fastener Reference Chart: Cross-reference the measurement of your bolt, nut or screw with these comprehensive table of sizes. Metric, Unified Thread Standard and British Thread Standards values matched. There are also simplified illustrations of how to identify metric or imperial fasteners by thread pitch and threads per inch, respectively.
  • Loctite Application Chart: Know which Loctite product to use with various materials and surfaces, from bricks and ceramics to vinyl and wood.
  • Pulley Size Chart: Sort through a wide variety of aluminium and cast-iron pulleys for different belt sections and grooves. For taper locks, pilot bores and bores with keyway. Metric and imperial sizes available.
  • Socket Sizing Cross-Reference Chart (Metric-Imperial Values): Match the right (or nearest alternative) sockets and drives. Metric and imperial sizes available.
  • Tapping Drill Size Chart for Thread Cutting Taps: Find the appropriate (and nearest alternative) drill size for creating a pilot hole before cutting threads in a workpiece. Common coarse and fine drill sizes listed. Metric and imperial (US decimal / fractional inches) values matched.

 

AIMS' Note on Safe Use of Hand Tools

  • Inspection: Before using any tool, carefully inspect it for cracks, chips, loose handles, worn / mushroomed heads or any other signs of damage. Damaged or defective tools may cause harm! Ensure all guards are in place.
  • Right tool for the job: Make sure you understand the intended purpose of each tool and choose the correct one for your specific job. Don't try to make a screwdriver work as a pry bar or a wrench as a hammer.
  • Safe handling: Carry sharp tools pointed down and away from your body. Never carry tools in your pockets where they can cause injury. When passing a tool to someone, extend the handle first.
  • PPE: Wear safety glasses or goggles to protect your eyes from flying debris. Consider gloves depending on the tool and task to prevent cuts or blisters but without compromising comfort, dexterity and protection. If working with noisy tools, wear ear protection.
  • Maintenance: Keep your tools clean, sharp and properly maintained. Store them in a safe and organised place when not in use.

spanners and wrenches