1.375 inches equals 34.925 millimeters, or 1 and 3/8 inches. That’s a hair longer than an inch and a third small enough to fit between two fingers, but big enough to matter in carpentry, hardware, and tool work.
Numbers on a screen are hard to picture. So below, you’ll find the exact conversion, a ruler breakdown, and 18 real objects that are roughly this size the kind of things you already own.
Table of Contents
How Long Is 1.375 Inches? (Quick Conversion)
Here’s the straight answer, broken into every unit you’re likely to need.
Unit
Value
Inches
1.375 in
Millimeters
34.925 mm
Centimeters
3.4925 cm
Feet
0.1146 ft
Yards
0.0382 yd
Fraction
1 ⅜ in
The math behind it is simple. One inch is defined as exactly 25.4 millimeters — a standard set by international agreement back in 1959 and still used by NIST today. So the formula is:
1.375 × 25.4 = 34.925 mm
In plain English: 1.375 inches is about 34.9 millimeters, or just under 3.5 centimeters. As a fraction, it’s written 1⅜ inches — a size you’ll see stamped on drill bits, washers, and pipe fittings throughout the U.S. hardware world.
What Does 1.375 Inches Look Like on a Ruler or Tape Measure?
This is where most conversion charts stop — and where the confusion usually starts. Here’s how to actually find 1.375 inches on a ruler.
Start at the 1-inch mark. On a standard imperial ruler, every inch is broken into 16 small tick marks, each representing 1/16 of an inch. You need 6 of those extra ticks past the 1-inch line, because 6/16 simplifies down to 3/8 — which is exactly 0.375.
So: 1.375 inches sits 3/8 of an inch past the 1-inch mark, roughly a third of the way to the 1.5-inch line.
What does .375 inches look like on its own? Picture the gap between the 3/8-inch tick and the very start of the ruler — it’s a short segment, a little wider than the tip of a standard pencil eraser. That’s the exact width you’re adding onto a full inch to get 1.375.
On a tape measure, the logic is identical, but the ticks are usually a bit bolder and color-coded at the half-inch and inch marks, which makes counting faster on a job site. Carpenters typically read this as “one and three-eighths” rather than the decimal — it’s the everyday language of framing squares, stud spacing, and trim work.
Converting the other direction: if you’re working in metric and wondering what 1.3 cm looks like, it’s just slightly shorter than 1.375 inches — about 13 millimeters, or roughly 0.51 inches. It’s a useful cross-check if your tools switch between imperial and metric scales mid-project.
18 Everyday Things That Are 1.375 Inches Long
Numbers stick better when they’re tied to something familiar. Below are 18 objects close to 1.375 inches, grouped by where you’d actually find them.
Object
Approx. Length
Category
Standard bottle cap
~1.2–1.4 in
Kitchen
Medium binder clip (wire width)
~1.37 in
Office
AAA battery
1.75 in (close reference)
Household
House key blade
~1.3–1.4 in
Everyday carry
USB-A connector
~1.4 in
Tech
Golf tee (short style)
~1.375 in
Sports
Adult thumb width at the knuckle
~1.3–1.4 in
Body reference
Standard paperclip (jumbo)
~1.4 in
Office
Chalk stick
~1.4 in
School
D-cell battery diameter
close but slightly wider
Household
Wine cork
~1.75 in length, similar diameter range
Kitchen
Roll of tape (core width)
~1.4 in
Office/craft
Standard door hinge pin
~1.375 in
Hardware
Finishing nail (long)
~1.375 in
Carpentry
Highlighter cap
~1.4 in
School
Small padlock body
~1.375 in
Security
Pocket knife handle width
~1.375 in
Everyday carry
Standard drawer knob diameter
~1.375 in
Furniture
Household and kitchen: A bottle cap and a wine cork are the two most reliable kitchen references — both objects most people touch daily without a second thought, making them a genuinely tool-free way to eyeball this length.
Office and school: A medium binder clip, a jumbo paperclip, and a piece of chalk all cluster near 1.375 inches. Office supply manufacturers keep these dimensions tight, so what’s in your desk drawer right now is a dependable stand-in.
Hardware and carpentry: This is where 1.375 inches shows up on purpose, not by accident. Finishing nails, door hinge pins, and certain drill bit and washer diameters are manufactured to this exact spec because trim work and cabinetry depend on consistent hole and fastener sizing.
Tech and everyday carry: A USB-A connector, a house key blade, and a pocket knife handle all fall in this range — objects you likely have on you right now, which makes them the fastest gut-check for this measurement.
Sports and recreation: A short golf tee lands close to 1.375 inches, engineered specifically for lower ball placement on fairway shots — a small but deliberate design choice by tee manufacturers.
Body reference: In a pinch, the width of an adult thumb at the knuckle is commonly cited as a rough 1.3–1.4-inch guide — not precise, but useful when no ruler is around.
It sits 3/8 of an inch past the 1-inch mark count 6 small tick marks (each 1/16 inch) beyond the “1” line on a standard ruler.
What does .375 inches look like?
It’s the short segment between zero and the 3/8-inch tick mark roughly the width of a pencil eraser tip, and the exact amount added to 1 inch to reach 1.375 inches.
How long is 1.375 in inches?
1.375 is already expressed in inches it equals 1 and 3/8 inches, or 34.925 millimeters when converted to metric.
What is 1.375 on a tape measure?
Look for the “1” mark, then count forward to the third small line past the half-inch mark tradespeople usually call this “one and three-eighths.”
What does 1.3 cm look like?
1.3 cm is about 0.51 inches noticeably shorter than 1.375 inches (3.49 cm), so the two aren’t interchangeable despite the similar-looking numbers.
Conclusion
1.375 inches equals 34.925 millimeters, or 1⅜ inches a size you’ll spot on rulers, tape measures, and dozens of everyday objects once you know where to look. Whether you’re framing trim, shopping for hardware, or just satisfying curiosity, you now have both the exact math and 18 real-world reference points to picture it instantly, no tools required.
Elizabeth Queen is a Owner and consumer research writer at HowLongThings.com, specializing in product lifespan, durability, and everyday household research. She’s passionate about helping readers make smarter, longer-lasting buying decisions.
