Fractional drill size chart (1/64–1 in)

    Every fractional drill from 1/64 to 1 inch in 1/64 steps, with its decimal and metric size, the nearest number/letter and metric drill, and the taps that call for it.

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    Fractional drills 1/64–1 in
    DrillInchmmNearest other drillsTap drill for
    1/640.01560.397#78 (0.0160) · 0.4 mm (0.0158)—
    1/320.03130.794#68 (0.0310) · 0.8 mm (0.0315)—
    3/640.04691.191#56 (0.0465) · 1.2 mm (0.0472)0-80
    1/160.06251.588#52 (0.0635) · 1.6 mm (0.0630)1-64 (50%)
    5/640.07811.984#47 (0.0785) · 2.0 mm (0.0787)2-56 (form)
    3/320.09382.381#42 (0.0935) · 2.4 mm (0.0945)—
    7/640.10942.778#35 (0.1100) · 2.8 mm (0.1102)5-40 (50%)
    1/80.12503.175#30 (0.1285) · 3.2 mm (0.1260)6-32 (form)
    9/640.14063.572#28 (0.1405) · 3.6 mm (0.1417)—
    5/320.15633.969#22 (0.1570) · 4.0 mm (0.1575)—
    11/640.17194.366#17 (0.1730) · 4.4 mm (0.1732)10-24 (form)
    3/160.18754.762#12 (0.1890) · 4.8 mm (0.1890)—
    13/640.20315.159#6 (0.2040) · 5.2 mm (0.2047)12-32 (form)
    7/320.21885.556#2 (0.2210) · 5.6 mm (0.2205)1/4-32, 1/4-20 (50%)
    15/640.23445.953Letter A (0.2340) · 6.0 mm (0.2362)1/4-28 (form), 1/4-32 (form)
    1/40.25006.350Letter E (0.2500) · 6.3 mm (0.2480)—
    17/640.26566.747Letter H (0.2660) · 6.7 mm (0.2638)—
    9/320.28137.144Letter K (0.2810) · 7.1 mm (0.2795)5/16-32, 5/16-24 (50%)
    19/640.29697.541Letter M (0.2950) · 7.5 mm (0.2953)5/16-32 (form)
    5/160.31257.938Letter O (0.3160) · 7.9 mm (0.3110)3/8-16
    21/640.32818.334Letter Q (0.3320) · 8.3 mm (0.3268)—
    11/320.34388.731Letter S (0.3480) · 8.7 mm (0.3425)3/8-32
    23/640.35949.128Letter T (0.3580) · 9.1 mm (0.3583)3/8-32 (form)
    3/80.37509.525Letter V (0.3770) · 9.5 mm (0.3740)—
    25/640.39069.922Letter W (0.3860) · 9.9 mm (0.3898)7/16-20, 7/16-14 (50%)
    13/320.406310.319Letter Y (0.4040) · 10.3 mm (0.4055)7/16-14 (form)
    27/640.421910.716Letter Z (0.4130) · 10.7 mm (0.4213)1/2-13, 7/16-28 (form)
    7/160.437511.112Letter Z (0.4130) · 11.1 mm (0.4370)—
    29/640.453111.509Letter Z (0.4130) · 11.5 mm (0.4528)1/2-20, 1/2-13 (50%)
    15/320.468811.906Letter Z (0.4130) · 11.9 mm (0.4685)1/2-28, 1/2-13 (form), 1/2-20 (50%)
    31/640.484412.303Letter Z (0.4130) · 12.3 mm (0.4843)9/16-12, 1/2-20 (form), 1/2-28 (form)
    1/20.500012.700Letter Z (0.4130) · 12.7 mm (0.5000)—
    33/640.515613.097Letter Z (0.4130) · 13.1 mm (0.5158)9/16-18, 9/16-24, 9/16-12 (50%)
    17/320.531313.494Letter Z (0.4130) · 13.5 mm (0.5315)5/8-11, 9/16-18 (form), 9/16-12 (form)
    35/640.546913.891Letter Z (0.4130) · 13.9 mm (0.5472)9/16-24 (form)
    9/160.562514.288Letter Z (0.4130) · 14.25 mm (0.5610)5/8-11 (50%)
    37/640.578114.684Letter Z (0.4130) · 14.75 mm (0.5807)5/8-18, 5/8-24, 5/8-11 (form)
    19/320.593815.081Letter Z (0.4130) · 15.0 mm (0.5906)5/8-18 (form), 5/8-18 (50%), 5/8-24 (50%)
    39/640.609415.478Letter Z (0.4130) · 15.5 mm (0.6102)5/8-24 (form)
    5/80.625015.875Letter Z (0.4130) · 15.75 mm (0.6201)—
    41/640.640616.272Letter Z (0.4130) · 16.25 mm (0.6398)11/16-24
    21/320.656316.669Letter Z (0.4130) · 16.75 mm (0.6594)3/4-10, 11/16-24 (50%)
    43/640.671917.066Letter Z (0.4130) · 17.0 mm (0.6693)11/16-24 (form)
    11/160.687517.463Letter Z (0.4130) · 17.5 mm (0.6890)3/4-16, 3/4-10 (50%)
    45/640.703117.859Letter Z (0.4130) · 17.75 mm (0.6988)3/4-20, 3/4-10 (form), 3/4-16 (50%)
    23/320.718818.256Letter Z (0.4130) · 18.25 mm (0.7185)3/4-16 (form), 3/4-20 (50%)
    47/640.734418.653Letter Z (0.4130) · 18.75 mm (0.7382)3/4-20 (form)
    3/40.750019.050Letter Z (0.4130) · 19.0 mm (0.7480)—
    49/640.765619.447Letter Z (0.4130) · 19.5 mm (0.7677)7/8-9, 13/16-20
    25/320.781319.844Letter Z (0.4130) · 19.75 mm (0.7776)13/16-20 (50%)
    51/640.796920.241Letter Z (0.4130) · 20.25 mm (0.7972)13/16-20 (form), 7/8-9 (50%)
    13/160.812520.638Letter Z (0.4130) · 20.75 mm (0.8169)7/8-14
    53/640.828121.034Letter Z (0.4130) · 21.0 mm (0.8268)7/8-20, 7/8-9 (form), 7/8-14 (50%)
    27/320.843821.431Letter Z (0.4130) · 21.5 mm (0.8465)7/8-14 (form), 7/8-20 (50%)
    55/640.859421.828Letter Z (0.4130) · 21.75 mm (0.8563)7/8-20 (form)
    7/80.875022.225Letter Z (0.4130) · 22.25 mm (0.8760)1"-8
    57/640.890622.622Letter Z (0.4130) · 22.5 mm (0.8858)15/16-20
    29/320.906323.019Letter Z (0.4130) · 23.0 mm (0.9055)15/16-20 (50%)
    59/640.921923.416Letter Z (0.4130) · 23.5 mm (0.9252)1-12, 15/16-20 (form), 1"-8 (50%)
    15/160.937523.813Letter Z (0.4130) · 23.75 mm (0.9350)1"-8 (form)
    61/640.953124.209Letter Z (0.4130) · 24.25 mm (0.9547)1-20, 1-12 (50%)
    31/320.968824.606Letter Z (0.4130) · 24.5 mm (0.9646)1-12 (form), 1-20 (50%)
    63/640.984425.003Letter Z (0.4130) · 25.0 mm (0.9842)1-1/8-7, 1-20 (form)
    11.000025.400Letter Z (0.4130) · 25.5 mm (1.0039)1-1/8-8

    Common questions

    What is 17/64 in decimal?
    0.2656 in (6.747 mm).
    What fractional drill is closest to a #7?
    13/64 in (0.2031 in) is 0.002 in over a #7 (0.201 in).

    Calculators that use this data

    Drill Chart & Size FinderNearest-drill finder over the full drill chart (#97-#1, A-Z, 1/64-4 in, 0.1-60 mm), drill speeds and pecks, Silver & Deming, aircraft and center drills, counterbores and reamer pre-drills.Tap Drill & Thread % CalculatorPercent of thread for any drill (cut and form taps), 75 / 65 / 50% tap drills, UNC / UNF / metric chart with thread limits, every thread to 4 in and M64, pipe taps and STI / Helicoil.Drilling CalculationsDrilling RPM, feed per revolution, point allowance and cutting time.

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