{
 "title": "Twist drill sizes: number, letter and fractional, with mm equivalents",
 "publisher": "MachinistCharts",
 "source": "https://machinistcharts.com/",
 "updated": "2026-10-06",
 "license": "CC BY 4.0, attribution: MachinistCharts (machinistcharts.com)",
 "method": "Number, letter and fractional twist drill diameters in decimal inch; mm = inch x 25.4. Nearest metric drill from a series in 0.05 mm steps below 3 mm and 0.1 mm steps from 3 mm. tap_drill_for lists the UNC/UNF threads on this site whose standard cut-tap drill is this size.",
 "standards": [
  "ASME B94.11M, Twist drills (number, letter, fractional and metric sizes)"
 ],
 "note": "Nominal drill diameters. A drilled hole usually cuts slightly oversize.",
 "rows": [
  {
   "series": "number",
   "drill": "#80",
   "inch": 0.0135,
   "mm": 0.34,
   "mm_exact": 0.3429,
   "nearest_metric_mm": 0.35,
   "nearest_metric_diff_mm": 0.007,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-80/"
  },
  {
   "series": "number",
   "drill": "#79",
   "inch": 0.0145,
   "mm": 0.37,
   "mm_exact": 0.3683,
   "nearest_metric_mm": 0.35,
   "nearest_metric_diff_mm": -0.018,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-79/"
  },
  {
   "series": "fractional",
   "drill": "1/64",
   "inch": 0.0156,
   "mm": 0.4,
   "mm_exact": 0.3969,
   "nearest_metric_mm": 0.4,
   "nearest_metric_diff_mm": 0.003,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/1-64-inch/"
  },
  {
   "series": "number",
   "drill": "#78",
   "inch": 0.016,
   "mm": 0.41,
   "mm_exact": 0.4064,
   "nearest_metric_mm": 0.4,
   "nearest_metric_diff_mm": -0.006,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-78/"
  },
  {
   "series": "number",
   "drill": "#77",
   "inch": 0.018,
   "mm": 0.46,
   "mm_exact": 0.4572,
   "nearest_metric_mm": 0.45,
   "nearest_metric_diff_mm": -0.007,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-77/"
  },
  {
   "series": "number",
   "drill": "#76",
   "inch": 0.02,
   "mm": 0.51,
   "mm_exact": 0.508,
   "nearest_metric_mm": 0.5,
   "nearest_metric_diff_mm": -0.008,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-76/"
  },
  {
   "series": "number",
   "drill": "#75",
   "inch": 0.021,
   "mm": 0.53,
   "mm_exact": 0.5334,
   "nearest_metric_mm": 0.55,
   "nearest_metric_diff_mm": 0.017,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-75/"
  },
  {
   "series": "number",
   "drill": "#74",
   "inch": 0.0225,
   "mm": 0.57,
   "mm_exact": 0.5715,
   "nearest_metric_mm": 0.55,
   "nearest_metric_diff_mm": -0.021,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-74/"
  },
  {
   "series": "number",
   "drill": "#73",
   "inch": 0.024,
   "mm": 0.61,
   "mm_exact": 0.6096,
   "nearest_metric_mm": 0.6,
   "nearest_metric_diff_mm": -0.01,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-73/"
  },
  {
   "series": "number",
   "drill": "#72",
   "inch": 0.025,
   "mm": 0.64,
   "mm_exact": 0.635,
   "nearest_metric_mm": 0.65,
   "nearest_metric_diff_mm": 0.015,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-72/"
  },
  {
   "series": "number",
   "drill": "#71",
   "inch": 0.026,
   "mm": 0.66,
   "mm_exact": 0.6604,
   "nearest_metric_mm": 0.65,
   "nearest_metric_diff_mm": -0.01,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-71/"
  },
  {
   "series": "number",
   "drill": "#70",
   "inch": 0.028,
   "mm": 0.71,
   "mm_exact": 0.7112,
   "nearest_metric_mm": 0.7,
   "nearest_metric_diff_mm": -0.011,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-70/"
  },
  {
   "series": "number",
   "drill": "#69",
   "inch": 0.0292,
   "mm": 0.74,
   "mm_exact": 0.7417,
   "nearest_metric_mm": 0.75,
   "nearest_metric_diff_mm": 0.008,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-69/"
  },
  {
   "series": "number",
   "drill": "#68",
   "inch": 0.031,
   "mm": 0.79,
   "mm_exact": 0.7874,
   "nearest_metric_mm": 0.8,
   "nearest_metric_diff_mm": 0.013,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-68/"
  },
  {
   "series": "fractional",
   "drill": "1/32",
   "inch": 0.0312,
   "mm": 0.79,
   "mm_exact": 0.7937,
   "nearest_metric_mm": 0.8,
   "nearest_metric_diff_mm": 0.006,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/1-32-inch/"
  },
  {
   "series": "number",
   "drill": "#67",
   "inch": 0.032,
   "mm": 0.81,
   "mm_exact": 0.8128,
   "nearest_metric_mm": 0.8,
   "nearest_metric_diff_mm": -0.013,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-67/"
  },
  {
   "series": "number",
   "drill": "#66",
   "inch": 0.033,
   "mm": 0.84,
   "mm_exact": 0.8382,
   "nearest_metric_mm": 0.85,
   "nearest_metric_diff_mm": 0.012,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-66/"
  },
  {
   "series": "number",
   "drill": "#65",
   "inch": 0.035,
   "mm": 0.89,
   "mm_exact": 0.889,
   "nearest_metric_mm": 0.9,
   "nearest_metric_diff_mm": 0.011,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-65/"
  },
  {
   "series": "number",
   "drill": "#64",
   "inch": 0.036,
   "mm": 0.91,
   "mm_exact": 0.9144,
   "nearest_metric_mm": 0.9,
   "nearest_metric_diff_mm": -0.014,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-64/"
  },
  {
   "series": "number",
   "drill": "#63",
   "inch": 0.037,
   "mm": 0.94,
   "mm_exact": 0.9398,
   "nearest_metric_mm": 0.95,
   "nearest_metric_diff_mm": 0.01,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-63/"
  },
  {
   "series": "number",
   "drill": "#62",
   "inch": 0.038,
   "mm": 0.97,
   "mm_exact": 0.9652,
   "nearest_metric_mm": 0.95,
   "nearest_metric_diff_mm": -0.015,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-62/"
  },
  {
   "series": "number",
   "drill": "#61",
   "inch": 0.039,
   "mm": 0.99,
   "mm_exact": 0.9906,
   "nearest_metric_mm": 1.0,
   "nearest_metric_diff_mm": 0.009,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-61/"
  },
  {
   "series": "number",
   "drill": "#60",
   "inch": 0.04,
   "mm": 1.02,
   "mm_exact": 1.016,
   "nearest_metric_mm": 1.0,
   "nearest_metric_diff_mm": -0.016,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-60/"
  },
  {
   "series": "number",
   "drill": "#59",
   "inch": 0.041,
   "mm": 1.04,
   "mm_exact": 1.0414,
   "nearest_metric_mm": 1.05,
   "nearest_metric_diff_mm": 0.009,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-59/"
  },
  {
   "series": "number",
   "drill": "#58",
   "inch": 0.042,
   "mm": 1.07,
   "mm_exact": 1.0668,
   "nearest_metric_mm": 1.05,
   "nearest_metric_diff_mm": -0.017,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-58/"
  },
  {
   "series": "number",
   "drill": "#57",
   "inch": 0.043,
   "mm": 1.09,
   "mm_exact": 1.0922,
   "nearest_metric_mm": 1.1,
   "nearest_metric_diff_mm": 0.008,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-57/"
  },
  {
   "series": "number",
   "drill": "#56",
   "inch": 0.0465,
   "mm": 1.18,
   "mm_exact": 1.1811,
   "nearest_metric_mm": 1.2,
   "nearest_metric_diff_mm": 0.019,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-56/"
  },
  {
   "series": "fractional",
   "drill": "3/64",
   "inch": 0.0469,
   "mm": 1.19,
   "mm_exact": 1.1906,
   "nearest_metric_mm": 1.2,
   "nearest_metric_diff_mm": 0.009,
   "tap_drill_for": "#0-80 UNF",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/3-64-inch/"
  },
  {
   "series": "number",
   "drill": "#55",
   "inch": 0.052,
   "mm": 1.32,
   "mm_exact": 1.3208,
   "nearest_metric_mm": 1.3,
   "nearest_metric_diff_mm": -0.021,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-55/"
  },
  {
   "series": "number",
   "drill": "#54",
   "inch": 0.055,
   "mm": 1.4,
   "mm_exact": 1.397,
   "nearest_metric_mm": 1.4,
   "nearest_metric_diff_mm": 0.003,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-54/"
  },
  {
   "series": "number",
   "drill": "#53",
   "inch": 0.0595,
   "mm": 1.51,
   "mm_exact": 1.5113,
   "nearest_metric_mm": 1.5,
   "nearest_metric_diff_mm": -0.011,
   "tap_drill_for": "#1-64 UNC; #1-72 UNF",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-53/"
  },
  {
   "series": "fractional",
   "drill": "1/16",
   "inch": 0.0625,
   "mm": 1.59,
   "mm_exact": 1.5875,
   "nearest_metric_mm": 1.6,
   "nearest_metric_diff_mm": 0.013,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/1-16-inch/"
  },
  {
   "series": "number",
   "drill": "#52",
   "inch": 0.0635,
   "mm": 1.61,
   "mm_exact": 1.6129,
   "nearest_metric_mm": 1.6,
   "nearest_metric_diff_mm": -0.013,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-52/"
  },
  {
   "series": "number",
   "drill": "#51",
   "inch": 0.067,
   "mm": 1.7,
   "mm_exact": 1.7018,
   "nearest_metric_mm": 1.7,
   "nearest_metric_diff_mm": -0.002,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-51/"
  },
  {
   "series": "number",
   "drill": "#50",
   "inch": 0.07,
   "mm": 1.78,
   "mm_exact": 1.778,
   "nearest_metric_mm": 1.8,
   "nearest_metric_diff_mm": 0.022,
   "tap_drill_for": "#2-56 UNC; #2-64 UNF",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-50/"
  },
  {
   "series": "number",
   "drill": "#49",
   "inch": 0.073,
   "mm": 1.85,
   "mm_exact": 1.8542,
   "nearest_metric_mm": 1.85,
   "nearest_metric_diff_mm": -0.004,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-49/"
  },
  {
   "series": "number",
   "drill": "#48",
   "inch": 0.076,
   "mm": 1.93,
   "mm_exact": 1.9304,
   "nearest_metric_mm": 1.95,
   "nearest_metric_diff_mm": 0.02,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-48/"
  },
  {
   "series": "fractional",
   "drill": "5/64",
   "inch": 0.0781,
   "mm": 1.98,
   "mm_exact": 1.9844,
   "nearest_metric_mm": 2.0,
   "nearest_metric_diff_mm": 0.016,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/5-64-inch/"
  },
  {
   "series": "number",
   "drill": "#47",
   "inch": 0.0785,
   "mm": 1.99,
   "mm_exact": 1.9939,
   "nearest_metric_mm": 2.0,
   "nearest_metric_diff_mm": 0.006,
   "tap_drill_for": "#3-48 UNC",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-47/"
  },
  {
   "series": "number",
   "drill": "#46",
   "inch": 0.081,
   "mm": 2.06,
   "mm_exact": 2.0574,
   "nearest_metric_mm": 2.05,
   "nearest_metric_diff_mm": -0.007,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-46/"
  },
  {
   "series": "number",
   "drill": "#45",
   "inch": 0.082,
   "mm": 2.08,
   "mm_exact": 2.0828,
   "nearest_metric_mm": 2.1,
   "nearest_metric_diff_mm": 0.017,
   "tap_drill_for": "#3-56 UNF",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-45/"
  },
  {
   "series": "number",
   "drill": "#44",
   "inch": 0.086,
   "mm": 2.18,
   "mm_exact": 2.1844,
   "nearest_metric_mm": 2.2,
   "nearest_metric_diff_mm": 0.016,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-44/"
  },
  {
   "series": "number",
   "drill": "#43",
   "inch": 0.089,
   "mm": 2.26,
   "mm_exact": 2.2606,
   "nearest_metric_mm": 2.25,
   "nearest_metric_diff_mm": -0.011,
   "tap_drill_for": "#4-40 UNC",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-43/"
  },
  {
   "series": "number",
   "drill": "#42",
   "inch": 0.0935,
   "mm": 2.37,
   "mm_exact": 2.3749,
   "nearest_metric_mm": 2.35,
   "nearest_metric_diff_mm": -0.025,
   "tap_drill_for": "#4-48 UNF",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-42/"
  },
  {
   "series": "fractional",
   "drill": "3/32",
   "inch": 0.0938,
   "mm": 2.38,
   "mm_exact": 2.3812,
   "nearest_metric_mm": 2.4,
   "nearest_metric_diff_mm": 0.019,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/3-32-inch/"
  },
  {
   "series": "number",
   "drill": "#41",
   "inch": 0.096,
   "mm": 2.44,
   "mm_exact": 2.4384,
   "nearest_metric_mm": 2.45,
   "nearest_metric_diff_mm": 0.012,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-41/"
  },
  {
   "series": "number",
   "drill": "#40",
   "inch": 0.098,
   "mm": 2.49,
   "mm_exact": 2.4892,
   "nearest_metric_mm": 2.5,
   "nearest_metric_diff_mm": 0.011,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-40/"
  },
  {
   "series": "number",
   "drill": "#39",
   "inch": 0.0995,
   "mm": 2.53,
   "mm_exact": 2.5273,
   "nearest_metric_mm": 2.55,
   "nearest_metric_diff_mm": 0.023,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-39/"
  },
  {
   "series": "number",
   "drill": "#38",
   "inch": 0.1015,
   "mm": 2.58,
   "mm_exact": 2.5781,
   "nearest_metric_mm": 2.6,
   "nearest_metric_diff_mm": 0.022,
   "tap_drill_for": "#5-40 UNC",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-38/"
  },
  {
   "series": "number",
   "drill": "#37",
   "inch": 0.104,
   "mm": 2.64,
   "mm_exact": 2.6416,
   "nearest_metric_mm": 2.65,
   "nearest_metric_diff_mm": 0.008,
   "tap_drill_for": "#5-44 UNF",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-37/"
  },
  {
   "series": "number",
   "drill": "#36",
   "inch": 0.1065,
   "mm": 2.71,
   "mm_exact": 2.7051,
   "nearest_metric_mm": 2.7,
   "nearest_metric_diff_mm": -0.005,
   "tap_drill_for": "#6-32 UNC",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-36/"
  },
  {
   "series": "fractional",
   "drill": "7/64",
   "inch": 0.1094,
   "mm": 2.78,
   "mm_exact": 2.7781,
   "nearest_metric_mm": 2.8,
   "nearest_metric_diff_mm": 0.022,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/7-64-inch/"
  },
  {
   "series": "number",
   "drill": "#35",
   "inch": 0.11,
   "mm": 2.79,
   "mm_exact": 2.794,
   "nearest_metric_mm": 2.8,
   "nearest_metric_diff_mm": 0.006,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-35/"
  },
  {
   "series": "number",
   "drill": "#34",
   "inch": 0.111,
   "mm": 2.82,
   "mm_exact": 2.8194,
   "nearest_metric_mm": 2.8,
   "nearest_metric_diff_mm": -0.019,
   "tap_drill_for": "",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-34/"
  },
  {
   "series": "number",
   "drill": "#33",
   "inch": 0.113,
   "mm": 2.87,
   "mm_exact": 2.8702,
   "nearest_metric_mm": 2.85,
   "nearest_metric_diff_mm": -0.02,
   "tap_drill_for": "#6-40 UNF",
   "same_size_as": "",
   "url": "https://machinistcharts.com/drill-size/number-33/"
  },
  {
   "series": "number",
   "drill": "#32",
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