# Length vs. Diameter — What's the Difference?

Edited by Tayyaba Rehman — By Fiza Rafique — Updated on November 5, 2023
Length is the measurement of something from end to end; diameter is the width of a circle across its center.

## Key Differences

Length refers to the extent of something from one end to the other, the longest dimension of an object. It is a fundamental measurement in various fields, from everyday use to scientific research.
Diameter is a specific term used to describe the straight-line distance passing through the center of a circle, connecting two points on the perimeter. It is twice the radius, another key measurement of a circle.
Length can be measured in units such as meters, feet, or miles, depending on the context and the extent of the distance being measured. It is a general concept and applies to lines, edges, and linear distances.
In contrast, diameter is strictly associated with the geometry of circles and spheres and is measured in the same units as length. The concept is critical in fields that deal with circular shapes and objects.
While length is a one-dimensional measurement, the concept of diameter gives a sense of scale to a two-dimensional shape (a circle) or a three-dimensional object (like a sphere or cylinder).

## Comparison Chart

### Definition

Measurement from end to end
Measurement across a circle's center

### Applicability

One-dimensional objects
Circular or spherical objects

### Units

Meters, feet, inches, etc.
Same as length, depends on context

### Geometric Association

Linear measurement
Related to circles and spheres

Not directly related

## Compare with Definitions

#### Length

Length is a measure of distance. In the International System of Quantities, length is a quantity with dimension distance.

#### Diameter

Twice the radius of a circle.
Calculate the diameter using the radius.

#### Length

The measurement of something from end to end.
The length of the table is two meters.

#### Diameter

A measurement used to describe the size of round objects.
The tree trunk had a massive diameter.

#### Length

The greater of two or the greatest of three dimensions of a body.
Measure the length of the room for the new carpet.

#### Diameter

A straight line reaching from one side of a circle or sphere to the opposite side, through the center.
The pipe's diameter determines its flow capacity.

#### Length

The extent of something along its longest side.
The length of the field is impressive.

#### Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle.

#### Length

A piece of something, such as rope or fabric, measured along its longest side.
Cut a length of wire for the project.

#### Diameter

A straight line segment passing through the center of a figure, especially of a circle or sphere, and terminating at the periphery.

#### Length

The duration or extent of time.
The movie's length was over two hours.

#### Diameter

The length of such a segment.

#### Length

The measurement or extent of something from end to end; the greater of two or the greatest of three dimensions of an object
The fish reaches a length of 10 inches
The delta is twenty kilometres in length

#### Diameter

Thickness or width.

#### Length

The amount of time occupied by something
Delivery must be within a reasonable length of time

#### Diameter

A unit of magnification equal to the number of times an object's linear dimensions is increased by the magnifying apparatus.

#### Length

A piece or stretch of something
The surviving length of track
A length of brown satin

#### Diameter

(geometry) Any straight line between two points on the circumference of a circle that passes through the centre/center of the circle.

#### Length

An extreme to which a course of action is taken
They go to great lengths to avoid the press

#### Diameter

(geometry) The length of such a line.

#### Length

The distance from the batsman at which a well-bowled ball pitches
Lewis tended to bowl short of a length

#### Diameter

(geometry) The maximum distance between any two points in a metric space

#### Length

(in bridge or whist) the number of cards of a suit held in one's hand, especially when five or more
To open one heart with equal length in hearts and spades is in the modern Acol style

#### Diameter

(graph theory) The maximum eccentricity over all vertices in a graph.

#### Length

The state, quality, or fact of being long. See Usage Note at strength.

#### Diameter

Any right line passing through the center of a figure or body, as a circle, conic section, sphere, cube, etc., and terminated by the opposite boundaries; a straight line which bisects a system of parallel chords drawn in a curve.

#### Length

The measurement of the extent of something along its greatest dimension
The length of the boat.

#### Diameter

The length of a straight line through the center of an object from side to side; width; thickness; as, the diameter of a tree or rock.

#### Length

A piece, often of a standard size, that is normally measured along its greatest dimension
A length of cloth.

#### Diameter

The distance through the lower part of the shaft of a column, used as a standard measure for all parts of the order. See Module.

#### Length

A measure used as a unit to estimate distances
Won the race by a length.

#### Diameter

The length of a straight line passing through the center of a circle and connecting two points on the circumference

#### Length

Extent or distance from beginning to end
The length of a novel.
The length of a journey.

#### Diameter

A straight line connecting the center of a circle with two points on its perimeter (or the center of a sphere with two points on its surface)

#### Length

The amount of time between specified moments; the duration
The length of a meeting.

#### Diameter

The line segment passing through the center of a circle, touching both edges.
Measure the diameter to find the circle's size.

#### Length

Often lengths Extent or degree to which an action or policy is carried
Went to great lengths to prove his point.

#### Diameter

The width of a circular object.
The diameter of the wheel is 22 inches.

#### Length

The duration of a vowel.

#### Length

The duration of a syllable.

#### Length

The vertical extent of a garment. Often used in combination
Knee-length.
Floor-length.

#### Length

The distance measured along the longest dimension of an object.

Duration.

#### Length

(horse racing) The length of a horse, used to indicate the distance between horses at the end of a race.

#### Length

(mathematics) Distance between the two ends of a line segment.

#### Length

(cricket) The distance down the pitch that the ball bounces on its way to the batsman.

#### Length

(figuratively) Total extent.
The length of a book

#### Length

Part of something that is long; a physical piece of something.
A length of rope

#### Length

(theatre) A unit of script length, comprising 42 lines.

#### Length

(bridge) The number of cards held in a particular suit.

#### Length

(obsolete) To lengthen.

#### Length

The longest, or longer, dimension of any object, in distinction from breadth or width; extent of anything from end to end; the longest line which can be drawn through a body, parallel to its sides; as, the length of a church, or of a ship; the length of a rope or line.

#### Length

A portion of space or of time considered as measured by its length; - often in the plural.
Large lengths of seas and shores.
The future but a length behind the past.

#### Length

The quality or state of being long, in space or time; extent; duration; as, some sea birds are remarkable for the length of their wings; he was tired by the length of the sermon, and the length of his walk.

#### Length

A single piece or subdivision of a series, or of a number of long pieces which may be connected together; as, a length of pipe; a length of fence.

#### Length

Detail or amplification; unfolding; continuance as, to pursue a subject to a great length.
May Heaven, great monarch, still augment your blissWith length of days, and every day like this.

#### Length

Distance.
He had marched to the length of Exeter.

To lengthen.

#### Length

The linear extent in space from one end to the other; the longest horizontal dimension of something that is fixed in place;
The length of the table was 5 feet

#### Length

Continuance in time;
The ceremony was of short duration
He complained about the length of time required

#### Length

The property of being the extent of something from beginning to end;
The editor limited the length of my article to 500 words

#### Length

Size of the gap between two places;
The distance from New York to Chicago
He determined the length of the shortest line segment joining the two points

#### Length

A section of something that is long and narrow;
A length of timber
A length of tubing

## Common Curiosities

#### Is diameter always longer than the radius?

Yes, diameter is twice as long as the radius.

#### What units are used to measure length?

Units like meters, feet, or miles can be used.

#### Are diameter and radius measured in the same units?

Yes, they are both measured in linear units.

#### What instruments measure length?

Rulers, tape measures, and laser measures can be used.

#### What does length measure?

Length measures the distance from one end to another.

#### Can length apply to shapes other than lines?

Yes, it can apply to the longest side of various shapes.

#### Is length a vector quantity?

No, it is a scalar quantity with magnitude only.

#### How is diameter defined?

Diameter is the width of a circle through its center.

#### Does diameter apply to spheres?

Yes, it describes a line through the center of a sphere.

#### Can diameter indicate the size of a pipe?

Yes, it often refers to the inner width of a pipe.

#### Do engineers use diameter for design?

Yes, particularly in designing cylindrical objects.

#### Is length used in time measurements?

Yes, it can describe the duration of events.

#### How do you find the diameter of a circle?

Measure across its center point to the opposite side.

#### Does length affect the area of a rectangle?

Yes, along with width, it determines the rectangle’s area.

Share via Social Media
Embed This Content
Embed Code
Share Directly via Messenger