1/16 as a Decimal

Long division: one divided by sixteen

1/16 as a decimal comes out of a single division: 1 divided by 16. Long division writes the digits one at a time, and because 16 is larger than 1, the first digit sits to the right of the decimal point.

The digits in order are 0, 6, 2 and 5, so the quotient is 0.0625 and the remainder of zero ends the division. Multiplying back confirms it: 0.0625 times 16 is exactly 1, which is what the fraction promises.

Four decimal places is not a coincidence. Sixteen is 2 to the fourth power, and each factor of 2 adds one terminating place to the decimal. That is why 1/2, 1/4, 1/8, 1/16, 1/32 and 1/64 all stop, while thirds, sixths, sevenths and ninths run on forever. A denominator with any prime factor other than 2 or 5 in it produces a repeating decimal, and 3, 7 and 9 all qualify.

Halving your way down from one half

Once the halving rhythm is visible, long division becomes optional. Start at 1/2, which is 0.5, and cut the value in half each time: 1/4 is 0.25, 1/8 is 0.125, 1/16 is 0.0625, 1/32 is 0.03125 and 1/64 is 0.015625. Every step adds one decimal place and doubles the denominator.

The number of decimal places equals the number of times 2 is multiplied to build the denominator, which is why the table reads like a ladder. It also explains why a machinist who works to a thousandth of an inch never needs more than four places to name a sixteenth, and why a 128th needs seven.

Going the other way is just as quick. A decimal of 0.0625 becomes 1/16 by counting four places and putting 625 over 10000, then dividing both parts by 625. The halving table skips that work entirely for the numbers that appear on a rule.

All sixteen marks, in order

The table lists every sixteenth of an inch with the shortest name for the same distance and the millimeter value that follows from it. The odd numerators are the ones that keep 16 on the bottom.

Half of those entries collapse into eighths and quarters, which is why a tape measure carries fewer labels than it has marks. The blade still has sixteen spaces, but the marks at 2/16, 4/16, 8/16 and 16/16 are the same lines as 1/8, 1/4, 1/2 and 1 inch, and they carry the shorter name.

The decimal column is worth memorizing at the quarter points: 0.25, 0.5 and 0.75, plus 0.0625 at the smallest mark. Those four numbers cover most of the readings a tape measure produces in a woodshop or on a framing crew.

Why the sixteenth is the shortest line

A standard inch rule splits each inch in half, then quarters, eighths and sixteenths, and the sixteenth marks are the shortest lines on the blade. Many tapes stop there, which makes 1/16 the smallest step you can read directly instead of estimating between lines. The sequence 1/2, 1/4, 1/8, 1/16, 1/32, 1/64 doubles the denominator at each step, and each new set of marks halves the gap between neighbours.

Counting is the practical skill. From one inch line to the next there are sixteen spaces, and the marks past a whole inch are counted one by one. A board cut at 12 13/16 inches is twelve whole inches plus thirteen marks past the 12 inch line, which is 0.8125 inch of the next inch, so the decimal reading is 12.8125 inches and the millimeter reading is 325.4375 mm. A shelf at 9 5/16 inches reads 9.3125 inches, or 236.5375 mm.

The lengths of the lines carry information. The half inch line is longest, the quarter lines come next, the eighth lines are shorter, and the sixteenth lines are shortest. When two marks look alike, count from the nearest numbered inch and use the half inch line as a checkpoint. The sixteenth marks on either side of a quarter line are the ones most often misread, because three short lines sit close together there.

1/16 inch in millimeters

The millimeter value follows from one fixed definition. NIST's Guide to the SI, Appendix B (2008, updated 2025) records the 1959 agreement that set the international yard at exactly 0.9144 meter, which puts the inch at exactly 25.4 millimeters. BIPM's SI Brochure, 9th edition (2019) lists the same factor among the units accepted for use with the SI.

Divide 25.4 by 16 and the result is 1.5875 millimeters, with no rounding anywhere in the chain, because both the inch and the millimeter are defined quantities rather than measured ones.

The nearest common drill size above the mark is 1.6 mm, which is 0.0125 mm wider than 1.5875 mm. That difference matters in a press fit and rarely matters in carpentry, where a sixteenth of an inch is 1.5875 mm and the saw kerf is wider than the error.

Metric rules divide the centimeter into ten millimeters, so a 1.5875 mm reading has no mark of its own on that side of the blade. The conversion is the only way to compare the two scales, and the factor is exact, so the comparison does not drift.

The sixteenth in feet, yards and thousandths

A sixteenth keeps its decimal no matter which unit carries it, because the fraction multiplies by whatever the whole unit is worth. One sixteenth of a foot is 0.0625 of 12 inches, which is 0.75 inch. One sixteenth of a yard is 0.0625 of 36 inches, which is 2.25 inches. One sixteenth of a mile is 0.0625 of 5,280 feet, which is 330 feet.

Machinists read the other direction. A micrometer reports thousandths of an inch, and 0.0625 inch is 62.5 thousandths, which sits halfway between the 62 and 63 lines on a scale marked that way. Written in ten thousandths the same length is 625, and a gauge reading of 0.062 or 0.063 inch brackets the mark from either side.

Framing layout keeps the fraction while metalwork keeps the decimal, and the two habits meet at the same number. Studs spaced 16 inches on center are 1.3333 feet apart, which is the 16 that gives the sixteenth its place in construction. The next time a blueprint calls out 0.4375, the rule calls it 7/16, and both names describe one distance.

Readings that land between two marks

Calipers and digital gauges report decimals, and those readings usually fall between two marks on the rule. Multiply the reading by 16 and round to the nearest whole number to find the mark.

A reading of 0.437 inch times 16 is 6.992, which rounds to 7, so the nearest mark is 7/16 inch at 0.4375. A reading of 0.69 inch times 16 is 11.04, so the mark is 11/16 at 0.6875. A reading of 0.31 inch times 16 is 4.96, so the mark is 5/16 at 0.3125.

Rounding to the nearest sixteenth leaves at most half a sixteenth of slack, which is 0.03125 inch, or 0.79375 mm. A rule marked in 32nds halves that again, and a caliper that reads to a thousandth does not need rounding at all until the number has to be written as a fraction.

The difference column is worth reading before choosing a mark. A reading of 0.93 inch is 0.0075 inch from 15/16, which is close to a fifth of a sixteenth, so the mark is a fair description of the measurement rather than an exact match. Quoting 15/16 as if it were exact claims more precision than the gauge provided.

1/16 is not 0.16

The digits in 1/16 invite a mistake that shows up on shop floors: reading the fraction as 0.16. The decimal 0.16 is 16/100, which reduces to 4/25, and it is 2.56 times larger than 0.0625. On a rule that is the difference between a fine line and a gap you can see across the bench.

The confusion comes from the denominator. Sixteen on the bottom means the inch is split into sixteen parts, not that the answer starts with the digits 1 and 6. Half of a tenth is 0.05, and 0.0625 lands between that and 0.075, so the true value is well under half of what 0.16 claims.

One multiplication settles it every time. 0.0625 times 16 returns exactly 1. If a decimal fails that test, it does not name a sixteenth of anything. The same test works for any fraction: multiply the decimal by the denominator and the answer should be the numerator, with no remainder.

A second check is the size of the number. Sixteenths of an inch are small, so the decimal must sit below 0.1 for any numerator under 1.6, and the only sixteenths above 0.5 are the last eight marks. A decimal like 0.16 sits between 1/8 and 3/16 on the rule, at 2.56 sixteenths, which is not a mark at all.