Metric to Inch Charts and Comparisons. US Dime Approx 18 mm in diameter and 1 mm thick. US Penny Approx 19 mm in diameter and 1.25 mm thick. US Nickel Approx 21 mm in diameter and 1.75 mm thick. US Quarter Approx 24 mm in diameter and 1.63 mm thick. Drop down conversion chart. metric/decimal/fraction conversions 1mm = .039" under 1/16" 2mm = .079" over 1/16" 3mm = .118" approx 1/8" 4mm = .158" under 5/32" 5mm = .197" over 3/16" 6mm = .236" under 1/4" 6.5mm = .255" over 1/4" 7mm = .276" over 1/4" 8mm = .315" under 5/16" 9mm = .354" under 3/8" 10mm = .394" over 3/8" 11mm = .433" under 7/16" 12mm = .472" under 1/2" 13mm = .512" over 1/2" 14mm = .551" under 9/16" 15mm = .591" under 5/8" 16mm = .630" over 5/8" 17mm = .669" under 11/16" 18mm = .709" over 11/16" 19mm = .748" under 3/4" 20mm = .787" under 13/16" 21mm = .827" over 13/16" 22mm = .866" under 7/8" 23mm = .906" under 15/16" 24mm = .945" over 15/16" 25mm = .984" under 1" 25.4mm = 1" exactly 1 inch 26mm = 1.024" over 1" 27mm = 1.063" 1-1/16" 28mm = 1.102" under 1-1/8" 29mm = 1.142" over 1-1/8" 30mm = 1.181" about 1-3/16" 31mm = 1.221" under 1-1/4" 32mm = 1.260" over 1-1/4" 33mm = 1.299" under 1-5/16" 34mm = 1.338" over 1-5/16" 35mm = 1.378" over 1-3/8" 36mm = 1.417" over 1-7/16" 37mm = 1.457" under 1-1/2" 38mm = 1.496" approx 1-1/2" 39mm = 1.535" over 1-1/2" 40mm = 1.575" over 1-9/16" 41mm = 1.614" approx 1-5/8" 42mm = 1.654" over 1-5/8" 43mm = 1.693" over 1-11/16" 44mm = 1.732" approx 1-1/2" 45mm = 1.772" over 1-1/2" 46mm = 1.811" approx 1-13/16" 47mm = 1.850" under 1-7/8" 48mm = 1.890" over 1/7/8" 49mm = 1.929" approx 1-15/16" 50mm = 1.969" approx 1-31/32" 50.8mm = 2" exactly 2 inch 51mm = 2.008" approx 2" 52mm = 2.047" approx 1-3/64" 53mm = 2.087" over 2-1/16" 54mm = 2.126 approx 2-1/8" 55mm = 2.165" over 2-5/32" 56mm = 2.205" over 2-3/16" 57mm = 2.244" approx 2-1/4" 58mm = 2.284 approx 2-9/16" 59mm = 2.323" under 2-7/8" 60mm = 2.362" approx 2-3/8" 61mm = 2.402" under 2-7/8" 62mm = 2.441" over 7/16" 63mm = 2.480" under 2-1/2" 64mm = 2.520" over 2-1/2" 65mm = 2.560" approx 2-9/16" 66mm = 2.598" under 2-5/8" 67mm = 2.638" approx 2-5/8" 68mm = 2.677" approx 2-11/16" 69mm = 2.717" over 2-11/16" 70mm = 2.756" approx 2-3/4" 71mm = 2.795" under 2-13/16" 72mm = 2.835" over 2-13/16" 73mm = 2.874" approx 2-7/8" 74mm = 2.913" under 2-15/16" 75mm = 2.953" over 2-15/16" 76mm = 2.992" under 3" 76.2mm = 3" exactly 3 inch 77mm = 3.032" over 3" 78mm = 3.071" over 3-1/16" 79mm = 3.110" approx 3-1/8" 80mm = 3.150" approx 3-5/32" Graduated mm to fractional inch chart. There are 25.4 millimeters in one inch. The Metric scale ranges from 0 to 25.4 mm. Tip. Use a ruler to help determine sizes. The fractional inch scale is in 16th's as on a common ruler. Graduated mm to decimal inch chart. There are 25.4 millimeters in one inch. The Metric scale ranges from 0 to 25.4 mm. The inch scale is in decimal inches. Please note. Metric and English units do not convert exactly. Use chart as a visual aid to compare millimeters (mm) to decimal inches.

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