Inches to Fraction Calculator
Convert any decimal length to a fractional inch measurement, ready to read straight off a tape measure. Enter a decimal, choose your precision, and get a simplified fraction — or convert from millimeters, centimeters or metres too.
✓ Precision from 1/2" to 1/256" ✓ Automatically simplifies fractions ✓ Works on mobile
Inches to Fraction Calculator
Why Convert Decimal Inches to Fractions?
Tape measures speak in fractions — this calculator translates for you.
Most measuring tools used in woodworking, construction, sewing and engineering — tape measures, rulers, calipers with a fractional scale — mark distances in fractions of an inch, like 3⁄8" or 11⁄16", rather than decimals like 0.375" or 0.6875". But many calculations, digital tools, and CAD programs naturally produce decimal results, which don't line up neatly with the marks on a physical tape measure.
An inches-to-fraction calculator bridges that gap: it takes a decimal length and converts it into the nearest fractional-inch measurement, at whatever precision your tool supports — typically 1/16", 1/32", or 1/64" for standard tape measures, and finer still for precision machining work. It also automatically simplifies the resulting fraction, so instead of an awkward result like 8/32", you get the cleaner, equivalent 1/4".
This calculator accepts decimal inches directly, or a length in millimeters, centimeters, or metres — converting to inches first using the standard 25.4 mm per inch relationship, then to the nearest fraction at your chosen precision.
Inches to Fraction Formula
The core rounding formula, and the metric conversion that precedes it.
Multiply the decimal part of the measurement (x) by your chosen denominator (d) — a power of 2, like 16 or 32 — and round to the nearest whole number to get the numerator (n).
The resulting inch fraction, before simplification. Combined with any whole-inch part, this gives the full measurement — for example, 32 13⁄16".
To convert from millimeters, divide by 25.4 first. For centimeters, divide by 2.54; for metres, divide by 0.0254.
Dividing both numerator and denominator by their greatest common divisor (GCD) reduces the fraction to its simplest equivalent form.
How the Inches to Fraction Calculator Works
Three steps to a tape-measure-ready result.
Choose Your Unit
Select inches, millimetres, centimetres, or metres depending on how your original measurement was taken.
Enter Your Value and Precision
Type in your decimal measurement, and choose a precision from 1/2" down to 1/256" to match your tool or project.
Automatic Calculation
The calculator converts to inches if needed, rounds to the nearest fraction at your chosen precision, and simplifies the result.
Read It Off the Ruler
See your result as a simplified fraction and a mixed number, with a live ruler diagram marking exactly where it falls.
Complete Guide to Converting Decimal Inches to Fractions
Where the rounding comes from, and how to convert from metric units.
Why Fractional Inches Use Powers of 2
Tape measures and rulers divide the inch in half repeatedly — into halves, quarters, eighths, sixteenths, and so on — because that's the easiest division to mark accurately and read visually by eye. This is why fraction-inch denominators are always a power of 2 (2, 4, 8, 16, 32, 64...) rather than an arbitrary number like 10 or 12; you'll essentially never see a measurement expressed in fifths or sevenths of an inch on a standard tool.
Converting a Decimal to a Fraction, Step by Step
Take the decimal part of your measurement (ignoring any whole inches for the moment), multiply it by your chosen denominator, and round the result to the nearest whole number — that becomes your numerator. For example, converting 11.81 inches at 1/16" precision: the decimal part 0.81 × 16 = 12.96, which rounds to 13, giving a fraction of 13/16, so the full measurement is 11 13/16 inches.
Converting from Millimeters, Centimeters or Metres First
If your original measurement is metric, convert it to inches before applying the fraction rounding: divide millimeters by 25.4, centimeters by 2.54, or metres by 0.0254. For example, 7 mm ÷ 25.4 = 0.2756 inches, which at 1/32" precision rounds to 9/32" (0.2756 × 32 = 8.82, rounding up to 9).
Why Precision Choice Matters
Choosing a coarser precision, like 1/8", rounds to the nearest eighth of an inch and is quick to read, but sacrifices accuracy — the true value could be off by up to 1/16" in either direction. Choosing a finer precision, like 1/64" or 1/128", captures much more accuracy but produces a more awkward-looking fraction that's harder to mark or read on a standard tape measure. Most everyday carpentry and DIY work is well served by 1/16" or 1/32" precision; machining and precision fabrication often calls for 1/64" or finer.
Why Simplifying the Fraction Matters
A raw rounded fraction like 8/32" is mathematically correct but unnecessarily awkward — it's exactly equivalent to the simpler 1/4", found by dividing both the numerator and denominator by their greatest common divisor (in this case, 8). Simplifying isn't just cosmetic: a simplified fraction is faster to read on a tape measure and less prone to transcription errors when a measurement gets written down or communicated to someone else.
Extracting Feet from a Long Inch Measurement
For measurements longer than 12 inches, it's common to express the result in feet and inches rather than a single large number of inches. Once you have a total inch measurement, divide by 12 to get whole feet, and the remainder (using the modulo operation) becomes the leftover inches — for example, 32 13/16" becomes 2' 8 13/16" once the whole feet are extracted.
Step-by-Step Inches to Fraction Examples
Eight worked conversions across common precisions and starting units.
Example 1 — Simple Decimal Conversion
Convert 11.81 inches to a fraction at 1/16" precision.
Example 2 — From Millimeters
Convert 12 mm to a fraction at 1/32" precision.
Example 3 — From Millimeters (Small Value)
Convert 7 mm to a fraction at 1/32" precision.
Example 4 — Fraction That Needs Simplifying
Convert 0.625 inches to a fraction at 1/32" precision.
Example 5 — Coarse Precision
Convert 3.4 inches to a fraction at 1/8" precision.
Example 6 — Fine Precision for Machining
Convert 0.2839 inches to a fraction at 1/64" precision.
Example 7 — Longer Board Measurement
A board is 32.81 inches long; convert to feet and inches at 1/16" precision.
Example 8 — From Metres
Divide a 5-metre board into 6 equal parts, and express one part as a fraction at 1/32" precision.
Fraction to Inches Conversion Table
Every 1/64" increment between 0" and 1", with millimeter equivalents.
| Fraction | Decimal (in) | Millimeters |
|---|---|---|
| 1/16" | 0.0625 | 1.5875 mm |
| 1/8" | 0.125 | 3.175 mm |
| 3/16" | 0.1875 | 4.7625 mm |
| 1/4" | 0.25 | 6.35 mm |
| 5/16" | 0.3125 | 7.9375 mm |
| 3/8" | 0.375 | 9.525 mm |
| 7/16" | 0.4375 | 11.1125 mm |
| 1/2" | 0.5 | 12.7 mm |
| 9/16" | 0.5625 | 14.2875 mm |
| 5/8" | 0.625 | 15.875 mm |
| 11/16" | 0.6875 | 17.4625 mm |
| 3/4" | 0.75 | 19.05 mm |
| 13/16" | 0.8125 | 20.6375 mm |
| 7/8" | 0.875 | 22.225 mm |
| 15/16" | 0.9375 | 23.8125 mm |
| 1" | 1.0 | 25.4 mm |
| Precision | Typical Use |
|---|---|
| 1/8", 1/16" | Rough carpentry, general DIY |
| 1/32" | Standard woodworking and construction |
| 1/64" | Fine woodworking, detailed trim work |
| 1/128", 1/256" | Precision machining and fabrication |
Benefits of Using an Inches to Fraction Calculator
Why reach for a dedicated tool instead of rounding by hand.
Instant, Accurate Results
Get a correctly rounded, simplified fraction the moment you enter a decimal value.
Automatic Simplification
Never deal with an awkward unsimplified fraction like 8/32" again — it's reduced to 1/4" automatically.
Multiple Metric Inputs
Convert directly from millimetres, centimetres or metres without a separate unit conversion step.
Adjustable Precision
Choose from 1/2" down to 1/256" to match your tape measure, project, or tolerance requirements.
Live Ruler Diagram
See exactly where your fraction falls on a ruler, for an intuitive visual check.
Mobile-Friendly
Use it right at the workbench or job site on any phone or tablet.
Practical Applications of Inches to Fraction Conversion
Where this conversion comes up in real measuring work.
Woodworking & Carpentry
Cutting lumber to precise fractional-inch lengths is a daily task for carpenters and woodworkers.
Construction & Building
Framing, trim work and layout measurements are typically read and marked in fractional inches on-site.
Machining & Precision Fabrication
Fine precision levels like 1/64" or 1/128" are essential when converting design decimals into shop-floor measurements.
Sewing & Fabric Work
Pattern measurements and seam allowances are often given in fractional inches on commercial patterns.
International Purchases
Converting a metric measurement to fractional inches when buying US-made hardware, tools or materials sized in inches.
CAD & Design Work
Converting decimal CAD output into shop-ready fractional dimensions before cutting or manufacturing.
Common Inches to Fraction Mistakes
Avoid these errors when converting decimal to fractional measurements.
Forgetting to simplify the fraction
A raw result like 8/32" is correct but unnecessarily awkward — always reduce to the simplest equivalent, like 1/4".
Choosing too coarse a precision
Rounding to 1/8" when 1/32" precision is actually needed can introduce a meaningful error for tight-tolerance work.
Mixing up which metric conversion factor to use
Millimeters divide by 25.4, centimeters by 2.54, and metres by 0.0254 — using the wrong factor shifts the decimal point entirely.
Rounding down instead of to the nearest value
The correct method rounds to the nearest whole numerator, not simply truncating — always round properly rather than dropping the decimal.
Forgetting to extract whole feet from a long measurement
A large inch value like 32.81" is usually clearer expressed as 2' 8 13/16" — don't leave it as an unwieldy number of inches.
Using a non-power-of-2 denominator
Standard tape measures only mark halves, quarters, eighths, sixteenths and so on — a denominator like 10 or 12 won't match any real-world tool.
Frequently Asked Questions
Everything people ask about converting inches to fractions.
How do I convert decimal inches to fractional inches?
Choose a denominator that's a power of 2 (like 16 or 32), multiply the decimal part of the measurement by that denominator, round to the nearest whole number to get the numerator, and express the result as numerator/denominator inches.
What's 12 mm to fractional inches?
12 mm converts to approximately 15/32 inch. First convert 12 mm to inches by dividing by 25.4 (giving about 0.4724 in), then round to the nearest 32nd.
How do I convert 7 mm to fractional inches?
7 mm ÷ 25.4 = 0.2756 in. At 1/32" precision, 0.2756 × 32 = 8.82, which rounds to 9, giving a result of 9/32 in.
What is 11.81 inches as a fraction?
11.81 inches is approximately 11 13/16 inches, using 16 as the denominator and rounding the decimal part accordingly.
Why does the calculator simplify the fraction?
A raw calculation might produce an unreduced fraction like 8/32" — simplifying it to 1/4" makes the result easier to read and mark accurately on a tape measure.
Why are fraction-inch denominators always powers of 2?
Because tape measures and rulers are marked by repeatedly halving the inch — into halves, quarters, eighths, sixteenths, and so on — rather than dividing into arbitrary fractions like fifths or tenths.
What precision should I use for woodworking?
Most woodworking and general DIY work is well served by 1/16" or 1/32" precision, while fine trim work or cabinetry may call for 1/64".
Can I convert centimeters or metres directly?
Yes. Select the appropriate unit tab, and the calculator converts to inches internally (dividing by 2.54 for cm or 0.0254 for m) before finding the fraction.
How accurate is this conversion?
The result is exact up to the rounding introduced by your chosen precision — a coarser precision like 1/8" can be off by up to 1/16" from the true decimal value, while finer precisions reduce that margin.
How do I express a long measurement in feet and inches?
Divide the total inches by 12 to get whole feet, and use the remainder as the leftover inches — for example, 32.81" becomes 2 ft 8 13/16".
Is there a difference between rounding up and rounding to the nearest value?
Yes — this calculator rounds to the nearest fractional value (standard rounding), which is more accurate than always rounding up, though some quick-reference guides use rounding up as a simpler approximation.
Can this calculator handle values greater than 1 inch?
Yes. The calculator separates the whole-inch portion from the fractional remainder automatically and returns a full mixed-number result.
Is this calculator accurate?
Yes. It applies the standard rounding formula used for fractional-inch conversion, along with the exact metric-to-inch conversion factors.
Is it free to use?
Yes, the Inches to Fraction Calculator is free, with no signup required.
Does it work on mobile?
Yes. The calculator and ruler diagram are fully responsive and work well on phones and tablets.
Convert Inches to Fraction Instantly
Enter a decimal length in any unit and get a clean, simplified fractional-inch measurement in seconds.