What Size Lies Between 3/8 and 7/16? A Detailed Guide to Fractional Measurements
When you’re working with screws, bolts, pipes, or any hardware, precise measurements matter. On top of that, the most common size that sits squarely in that gap is 13/32 inch (0. If you’ve ever looked at a chart of fractional inch sizes and wondered what fits between 3/8 inch (0.That's why 40625 in). In practice, 375 in) and 7/16 inch (0. And 4375 in), you’re not alone. Understanding why 13/32 in is the logical choice, how it relates to other fractions, and where you’ll encounter it in real‑world projects can save you time, avoid costly mistakes, and give you confidence when selecting the right hardware And that's really what it comes down to..
Introduction
In the world of DIY, carpentry, metalworking, and even culinary measurements, fractions are a everyday language. The question “what size is between 3/8 and 7/16?” often pops up when you need a bolt, a drill bit, or a pipe that doesn’t match the two obvious fractions.
Not the most exciting part, but easily the most useful.
- The exact fractional and metric equivalents of the size that falls between 3/8 in and 7/16 in.
- How to read fraction charts and why 13/32 in is the standard choice.
- Where you’ll encounter 13/32 in in tools, fasteners, and piping systems.
- Simple tips for measuring and verifying the size you need.
Understanding Fractional Inches
How Fractions Work
Fractions represent parts of a whole. In inch measurements, the denominator tells you how many equal parts the inch is divided into, while the numerator tells you how many of those parts you have. For example:
- 3/8 in = three parts out of eight equal parts of an inch.
- 7/16 in = seven parts out of sixteen equal parts of an inch.
Because the denominators differ, you need a common denominator to compare them directly. The smallest common denominator for 8 and 16 is 16. Converting:
- 3/8 in = (3 × 2)/(8 × 2) = 6/16 in
- 7/16 in = 7/16 in
Now you can see the gap: 6/16 in to 7/16 in. The next logical step is to find a fraction with a denominator of 32 (the next power of two) that lands between 6/16 and 7/16. Multiplying numerator and denominator by 2 gives:
People argue about this. Here's where I land on it.
- 6/16 in = 12/32 in
- 7/16 in = 14/32 in
The only whole‑number numerator that fits between 12 and 14 is 13, giving us 13/32 in. This is why 13/32 in is universally recognized as the size “between” 3/8 in and 7/16 in.
Converting to Decimal and Metric
| Fraction | Decimal (inches) | Millimeters |
|---|---|---|
| 3/8 in | 0.3750 | 9.525 mm |
| 13/32 in | 0.40625 | 10.That said, 31875 mm |
| 7/16 in | 0. 4375 | 11. |
The metric conversion is handy when you’re working with international tools or specifications. But 13/32 in ≈ 10. 32 mm, a size you’ll often see labeled as “M10” in metric bolt charts.
Where You’ll Encounter 13/32 in
Fasteners and Screws
Many bolt and screw sets include a 13/32 in size because it fills a common gap between larger and smaller hardware. For example:
- Wood screws – 13/32 in is a popular size for joining medium‑thick lumber.
- Machine bolts – In older American hardware, a 13/32 in bolt may be used for heavy‑duty applications where a 3/8 in bolt is too small and a 7/16 in bolt is too large.
Drill Bits and Cutting Tools
Drill bit sets often list 13/32 in as a standard size for drilling holes that will receive 13/32 in bolts or pins. It’s also used for:
- Hole saws – A 13/32 in hole saw can cut through wood or metal to create openings for wiring or plumbing.
- Screwdrivers – Some Phillips and flat‑head drivers come in 13/32 in head sizes for specialized screws.
Plumbing and Piping
In older plumbing systems, especially those using national pipe thread (NPT), a 13/32 in pipe might appear as a transition piece between 3/8 in and 7/16 in connections. Although modern plumbing often uses metric sizes, vintage fixtures and restoration projects frequently require the exact 13/32 in thread Most people skip this — try not to..
Automotive and Motorcycle Parts
Classic cars and motorcycles sometimes use 13/32 in nuts and bolts for components like throttle cables, brake lines, or suspension mounts. Knowing the correct size helps preserve authenticity when restoring these vehicles.
Practical Tips for Working with 13/32 in
1. Identify the Size Quickly
- Use a fractional ruler – Most rulers have markings for 1/32 in increments. 13/32 in sits exactly halfway between the 12/32 (3/8) and 14/32 (7/16) marks.
- Check tool charts – Screwdriver, drill bit, and socket sets often include a small table that lists the corresponding sizes.
2. Verify with a Caliper
A digital caliper can confirm the exact dimension. If the reading is close to 0.Place the jaws around the shank of a bolt or the diameter of a drill bit. 40625 in (or 10.32 mm), you have the right size That's the whole idea..
3. Convert When Needed
If you’re working with metric tools, remember:
- 13/32 in × 25.4 = 10.31875 mm
- Round to 10.32 mm for most practical purposes.
4. Avoid Common Mistakes
- Mixing up fractions – Always double‑check that you’re not confusing 13/32 in with 5/12 in (≈0.4167 in). The latter is slightly larger and not interchangeable
