Fraction to Decimal Chart
Complete fraction to decimal conversion chart with millimeter equivalents for every 64th of an inch. Search any fraction or decimal, filter by resolution, sort by any column, and print for your shop wall.
A fraction to decimal chart converts fractional inch dimensions to their decimal and millimeter equivalents. This table covers all 64 fractions from 1/64" (0.015625") through 1" (1.0000"), each shown in simplest reduced form. To convert any fraction to a decimal, divide the numerator by the denominator: for example, 3/8 = 3 ÷ 8 = 0.375". To convert inches to millimeters, multiply by 25.4. Use the search field to look up any fraction or decimal instantly — this chart works for both fraction-to-decimal and decimal-to-fraction conversion.
Source: Fraction-to-decimal values are exact mathematical conversions (numerator ÷ denominator). Millimeter values use the defined factor 1 inch = 25.4 mm per the International Yard and Pound Agreement (1959). Cross-referenced with Machinery’s Handbook 29th Ed., pp. 28–30.
How to Use This Fraction to Decimal Chart
Type any fraction (like 3/8) or decimal (like 0.375) into the Search field to find its equivalent instantly. Click any table value to copy it to your clipboard. Click a row to highlight it for reference.
For dimensions greater than 1 inch, add the whole number to the fractional decimal. For example, 2-3/8" = 2 + 0.375 = 2.375". For drill bit sizes in fractional, number, and letter series, see our drill bit size chart.
If you need the correct tap drill size for a threaded hole, see our tap drill size chart, which maps thread sizes to drill diameters at adjustable engagement percentages.
Example: Converting 7/16" to Decimal and Millimeters
A drawing calls out a 7/16" slot width. To find the decimal equivalent: 7 ÷ 16 = 0.4375". To convert to millimeters: 0.4375 × 25.4 = 11.1125 mm. Search “7/16” in the chart above to confirm both values.
Example: Finding the Fraction for 0.3125"
Your caliper reads 0.3125" and you need the fractional equivalent. Multiply by 64: 0.3125 × 64 = 20. So the dimension is 20/64", which simplifies to 5/16". You can also type “0.3125” in the search field to find it directly. For a part drawing, you would call this out as 5/16" (the reduced form).
Frequently Asked Questions
How do I convert a fraction to a decimal?
Divide the numerator (top number) by the denominator (bottom number). For example, 3/8 = 3 ÷ 8 = 0.375. For fractions of an inch, this chart shows the exact decimal equivalent for every 64th of an inch, from 1/64 (0.015625) through 1 inch. Any fraction can be converted this way: 5/16 = 5 ÷ 16 = 0.3125, 7/32 = 7 ÷ 32 = 0.21875.
How do I convert a decimal to a fraction?
Multiply the decimal by 64 to find the nearest 64th of an inch, then simplify. For example, 0.375 × 64 = 24, so 0.375 = 24/64 = 3/8. For decimals that don’t divide evenly into 64ths, round to the nearest whole number: 0.200 × 64 = 12.8, so the closest fraction is 13/64 (0.203125). Use the search field above to type any decimal and find the nearest fraction instantly.
How do I convert fractions of an inch to millimeters?
Multiply the decimal equivalent by 25.4, since one inch is defined as exactly 25.4 millimeters. For example, 3/8 inch = 0.375 × 25.4 = 9.525 mm. This conversion factor is exact — it was established by the International Yard and Pound Agreement of 1959. The mm column in this chart shows the millimeter equivalent for every fraction.
Can I print this fraction to decimal chart?
Yes. Click the Print / PDF button above the table. The print layout removes interactive controls and formats the table for standard paper. You can print directly or save as a PDF. Use the Resolution filter to select which fractions to include — choose 8ths for a compact reference card, 16ths for a standard shop chart, or All (64ths) for the complete table.
What is the smallest standard fraction of an inch?
The finest standard fractional increment is 1/64 of an inch, equal to 0.015625 inches (0.397 mm). This is the smallest fraction shown on engineering fraction-to-decimal charts and matches the spacing of fractional drill sizes per ANSI/ASME B94.11M. For dimensions smaller than 1/64 inch, machinists and engineers use decimal inches (thousandths) or metric millimeters.
Related Calculators
- Drill Bit Size Chart — Complete chart of number, letter, fractional, and metric drill sizes with decimal equivalents
- Tap Drill Size Chart — Find the correct drill for tapping UNC, UNF, and metric threads
- Sheet Metal Gauge Chart — Gauge numbers to fractional and decimal inch thicknesses for steel, stainless, and aluminum
- Pipe Schedule Chart — Pipe dimensions, wall thickness, and weight per foot by schedule
References
- Oberg, E. et al. Machinery’s Handbook, 29th Edition, Industrial Press, 2012, pp. 28–30. Decimal Equivalents of Fractions tables (cross-reference for values derived from exact mathematical division).
- International Yard and Pound Agreement (1959) — Defines 1 inch = 25.4 mm exactly. Codified in NIST Handbook 44, Appendix C.
- ANSI/ASME B94.11M-1993 — Twist Drills (Inch and Metric). Defines fractional drill sizes in 1/64" increments, establishing 1/64" as the standard minimum fractional resolution.
Data last verified: March 2026
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