Inches to Fraction Converter
1.375 inches rounds to 1 3/8 inches on a tape measure. This inches to fraction converter turns decimal inches into the nearest common shop fraction, from halves through 64ths. Switch modes to enter a mixed fraction like 2 5/16 and turn it back into decimal inches for layouts, cut lists, drawings, and drill charts.
Quick answer
Pick the denominator that matches your tape, rule, or print, such as 1/16 or 1/32.
Match the rounding step to your tape, rule, print, or drill chart.
Result
1 3/8 in
Decimal inches
1.375 in
Rounded decimal
1.375 in
Precision
Nearest 1/16 in
What this tells you
- •Pick the denominator that matches your tape, rule, or print, such as 1/16 or 1/32.
- •The converter rounds the decimal part of the inch to the nearest mark at that precision.
- •Fraction results are simplified, so 26/64 shows as 13/32.
- •Mixed fractions like 1 3/8, simple fractions like 3/4, and whole inches all parse in reverse mode.
How to Use
- 1Choose decimal to fraction or fraction to decimal mode.
- 2Enter the inch value or mixed fraction.
- 3Select the denominator you want to round to, from 2 through 64.
- 4Read the nearest fraction and decimal inch values below.
How It Works
Formula
nearest fraction = whole inches + round(decimal part × denominator) / denominatorSplit the measurement into whole inches and the decimal remainder. Multiply the remainder by the selected denominator, round to the nearest whole numerator, then simplify the fraction. To go back to decimal inches, add the whole inches to the numerator divided by the denominator. For example, 2.3125 inches at 1/16 precision gives 0.3125 × 16 = 5, so the result is 2 5/16 inches.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Convert 1.375 inches to a fraction
0.375 inches is 6/16, which simplifies to 3/8, so the nearest 1/16 mark is 1 3/8 in.
Convert 0.40625 inches to a fraction
0.40625 inches is 26/64, which simplifies to 13/32 while keeping 1/64 precision.
Convert 2 5/16 inches to decimal
Add the whole inches to 5 divided by 16. That gives 2 + 0.3125 = 2.3125 inches.
Common Decimal Inch Equivalents
Handy shop and construction fractions you see on rules, tapes, and drill charts.
| Decimal inches | Nearest fraction | Nearest 64th mark |
|---|---|---|
| 0.125 | 1/8 in | 8/64 in |
| 0.1875 | 3/16 in | 12/64 in |
| 0.375 | 3/8 in | 24/64 in |
| 0.625 | 5/8 in | 40/64 in |
| 0.8125 | 13/16 in | 52/64 in |
| 1.375 | 1 3/8 in | 1 24/64 in |
| 2.3125 | 2 5/16 in | 2 20/64 in |
Fractions are simplified in the result card, even when the rounding step is 1/32 or 1/64.
How fractional-inch rounding works
The selected denominator sets the spacing between possible marks before simplification. Nearest 1/2 allows whole and half-inch positions. Nearest 1/16 allows sixteen positions per inch, and nearest 1/64 allows sixty-four. A finer setting usually stays closer to the decimal input. It can also imply more measurement precision than the ruler, material, saw, or process can support, so choose a setting that matches the actual work.
The converter splits the absolute value into whole inches and a decimal remainder. It multiplies that remainder by the selected denominator and rounds to the nearest integer numerator. For 2.2 at quarter-inch precision, 0.2 times 4 equals 0.8, which rounds to 1. The nearest fraction is therefore 2 1/4 in, and the rounded decimal is 2.25 in. A negative sign is restored after this calculation when the original measurement is below zero.
Simplification changes the written fraction without changing its position. A remainder of 0.375 produces 6/16 at sixteenth-inch precision. Dividing both numerator and denominator by 2 gives 3/8, which names the same ruler mark. This is why a result rounded on a 1/64 grid may display with a denominator of 32, 16, 8, 4, or 2.
Rounding can cross a whole-inch boundary. At sixteenth-inch precision, the remainder in 2.99 produces 15.84 sixteenths, which rounds to 16/16. The converter carries that full fraction into the whole-number part and displays 3 in instead of 2 16/16 in. The rounded decimal also becomes 3.
Reverse mode separates parsing from the nearest-mark result. Entering 1/3 produces an original decimal of about 0.333333 in. With 1/16 selected, the nearest available fraction is 5/16 and the rounded decimal is 0.3125. The selected denominator does not change the value parsed from the fraction text. It controls only the rounded fraction and rounded-decimal lines.
Signed whole numbers, decimals, simple fractions, and mixed fractions are accepted in reverse mode. The parser also removes common inch labels and straight or curly quotation marks. A minus sign before a mixed number applies to the entire value, so -1 1/2 becomes -1.5. Feet notation, Unicode fraction characters, and tolerance expressions need to be converted or separated before entry.
Common mistakes
- Picking the wrong denominator for the job. Cabinet layouts often use 1/32 while framing tape calls usually stop at 1/16.
- Reading the decimal digits as a fraction. 1.375 inches is not 1 and 375 over 1000. It is 1 and 3/8 inches.
- Rounding twice. Keep the original decimal until the last step, especially when you are stacking several cuts or offsets.
- Assuming the displayed denominator must match the selected precision. The converter simplifies after rounding, so 26/64 displays as the equal fraction 13/32.
- Missing the whole-inch carry. A remainder that rounds to 16/16, 32/32, or 64/64 becomes another whole inch.
- Entering feet-and-inch notation in reverse mode. Text such as 5 ft 3 in is not supported, so separate the feet before entering inches.
- Ignoring the sign on a negative mixed number. The input -1 1/2 means negative 1.5, not negative 1 plus positive 1/2.
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