80 mm to Inches
Convert 80 millimeters to inches — instant, accurate, and easy
The Answer
Browse metric rulers on Amazon.
📄 Free printable mm to inches chart (PDF) — every mm from 1 to 300.
How to Convert 80 mm to Inches
To convert 80 millimeters to inches, divide the millimeter value by 25.4. This is because one inch equals exactly 25.4 millimeters — a standard defined by international agreement.
The Calculation
Applying the formula to 80 mm:
Result Summary for 80 mm
- Decimal inches: 3.1496″
- Fractional inches: 3 5/32″ (nearest 1/64)
- Feet and inches: 0 ft 3.15 in
Which Tape Mark Is Closest to 80 mm?
80 mm is between 3 1/8 and 3 3/16 inches. A tape with 1/16-inch divisions rounds it to 3 1/8 inches, while a finer 1/32-inch scale rounds it to 3 5/32 inches.
Find the Mark Step by Step
Count three full inches, then five 1/32-inch divisions. That is 3 5/32 inches. The exact 80 mm point is 0.16875 mm before this mark.
The Tape Marks on Either Side
| Position | Tape mark | Mark in mm | Difference from 80 mm |
|---|---|---|---|
| Lower 1/16-inch mark | 3 1/8″ | 79.375 mm | −0.625 mm |
| Upper 1/16-inch mark | 3 3/16″ | 80.9625 mm | +0.9625 mm |
Positive differences are longer than 80 mm; negative differences are shorter. These are conversion rounding differences, not the accuracy of a measuring tool.
A Practical Example
For four 80 mm intervals, the required total is 320 mm. Four 3 1/8-inch intervals give 317.5 mm, falling short by 2.5 mm. Four 3 5/32-inch intervals give 320.675 mm, exceeding it by 0.675 mm.
For repeated hole spacing, measure each location from a common starting point in millimeters. Repeating a rounded inch interval can accumulate a larger error across the layout.
For the full method, see how to read inch and millimeter tape markings. For other sizes, use the millimeter-to-inch conversion chart and printable table.
Calculation basis: inches = millimeters ÷ 25.4. NIST defines one inch as exactly 25.4 mm. Decimal results and tape fractions shown here are rounded.
Reference Table — Values Near 80 mm
| Millimeters | Decimal Inches | Fractional Inches |
|---|---|---|
| 77 mm | 3.0315″ | 3 1/32″ |
| 78 mm | 3.0709″ | 3 5/64″ |
| 79 mm | 3.1102″ | 3 7/64″ |
| 80 mm | 3.1496″ | 3 5/32″ |
| 81 mm | 3.1890″ | 3 3/16″ |
| 82 mm | 3.2283″ | 3 15/64″ |
| 83 mm | 3.2677″ | 3 17/64″ |
80 mm in Other Units
Millimeters convert cleanly into every other length unit. Here is 80 mm expressed seven different ways — useful when a drawing, spec sheet or supplier quotes a unit other than inches.
| Unit | 80 mm equals |
|---|---|
| Centimeters (cm) | 8 cm |
| Meters (m) | 0.08 m |
| Inches (in) | 3.1496 in |
| Feet (ft) | 0.2625 ft |
| Yards (yd) | 0.08749 yd |
| Thousandths of an inch (mil) | 3,149.6 mil |
| Typographic points (1/72 in) | 226.77 pt |
How Accurate Is Each Fraction of 80 mm?
80 mm equals 3.1496″ (rounded to four decimal places). Any fraction is a further rounding of the full-precision value, so each one carries a small error. This table shows the closest fraction at each common denominator and how far it actually sits from 80 mm.
| Rounded to | Fraction | Decimal | Fraction vs. original |
|---|---|---|---|
| Nearest 1/2″ | 3″ | 3.0000″ | −3.800 mm (below original) |
| Nearest 1/4″ | 3 1/4″ | 3.2500″ | +2.550 mm (above original) |
| Nearest 1/8″ | 3 1/8″ | 3.1250″ | −0.625 mm (below original) |
| Nearest 1/16″ | 3 1/8″ | 3.1250″ | −0.625 mm (below original) |
| Nearest 1/32″ | 3 5/32″ | 3.1563″ | +0.169 mm (above original) |
| Nearest 1/64″ | 3 5/32″ | 3.1563″ | +0.169 mm (above original) |
For woodworking, DIY and general workshop use, 3 5/32″ is the practical choice — it lands within 0.4 mm of 80 mm. For machining, toolmaking or CAD, use the decimal value 3.1496″ rather than any fraction.
FAQ About 80 mm to Inches
How many inches is 80 mm?
80 millimeters equals 3.1496 inches (rounded to 4 decimal places), or approximately 3 5/32″ (nearest 1/64 inch).
How accurate is the 80 mm to inches conversion?
The conversion of 80 mm to 3.1496 inches uses the exact definition 1 inch = 25.4 millimeters; the four-decimal result is rounded, so it is approximate.
Can I convert 80 mm to feet?
Yes. 80 millimeters equals approximately 0 ft 3.15 in.
📏 Need to measure 80mm accurately?
A steel ruler marked in millimeters makes it easy to find 80 mm (≈ 3.1496″). See current options:
→ See precision steel rulers on Amazon
Or step up to a digital caliper for finer work →
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🔧 Recommended Tools to Measure 80mm
For precision measurements: A digital caliper is a handy option: most models display readings to 0.01 mm resolution and switch between millimeters and inches.
→ Our top pick: Adoric Digital Caliper 0-6″
See full guide: Digital Calipers Buying Guide
For longer measurements around the home: A quality 25ft tape measure covers most household and workshop needs.
→ Our top pick: CRAFTSMAN 25-Ft Tape Measure
See full guide: 25ft Tape Measure Buying Guide
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