Litre symbol

A capital or lower-case L, the symbol for the litre.

Also known as: Liter symbol

ScientificEveryday & digitalPackaging & recyclingStandard profile

Meanings

The litre is accepted for use with the SI without being an SI unit, and it is the one unit whose symbol may be written either upper or lower case — because a lower-case l is too easily read as a digit one.

Common modern usageVerified fact
Denotes the litre, a unit of volume equal to one cubic decimetre, accepted for use with the SI without being an SI unit itself.
Contexts: Mathematics
Officially standardisedVerified fact
May be written as either a capital or a lower-case L. It is the sole exception the SI makes to its capitalisation rules, allowed because a lower-case l is easily mistaken for the digit one in many typefaces.
Contexts: Mathematics
Common modern usageVerified fact
Appears on packaging as L, l or ml for volume declarations, and is the unit most readers meet the milli prefix through.
Contexts: Packaging

Visual description

The Latin letter L: as a capital, a vertical stroke with a horizontal foot extending to the right; as a lower-case letter, a plain vertical stroke with an ascender.

Symmetry: none
Orientation: upright

Confidence

IdentityHigh confidence: High confidence because the identity is defined by a current official standard, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is defined by a current official standard, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

Litre
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for origin narrative and for units the SI does not define, never for an official-definition claim.
Metric prefix
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for origin narrative and for units the SI does not define, never for an official-definition claim.
Guide for the Use of the International System of Units (SI), NIST Special Publication 811
National Institute of Standards and Technology · retrieved 2026-07-31
A national metrology institute's guidance on applying the SI, including symbol formatting. Authoritative for usage rules in the United States; it interprets the SI rather than defining it.
The International System of Units (SI), 9th edition
Bureau International des Poids et Mesures · retrieved 2026-07-31
The defining document for SI unit names and symbols, including the capitalisation and spacing rules. It defines units; it says nothing about how a symbol is encoded in a character set, and nothing about non-SI units except where it lists those accepted for use with the SI.

Last reviewed 2026-08-01

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Units of measurement and their symbols

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Meanings

Common modern usageVerified fact

Denotes the litre, a unit of volume equal to one cubic decimetre, accepted for use with the SI without being an SI unit itself.

Contexts: Mathematics

Officially standardisedVerified fact

May be written as either a capital or a lower-case L. It is the sole exception the SI makes to its capitalisation rules, allowed because a lower-case l is easily mistaken for the digit one in many typefaces.

Contexts: Mathematics

Common modern usageVerified fact

Appears on packaging as L, l or ml for volume declarations, and is the unit most readers meet the milli prefix through.

Contexts: Packaging

Confidence

IdentityHigh confidence: High confidence because the identity is defined by a current official standard, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is defined by a current official standard, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

Litre
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for origin narrative and for units the SI does not define, never for an official-definition claim.
Metric prefix
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for origin narrative and for units the SI does not define, never for an official-definition claim.
Guide for the Use of the International System of Units (SI), NIST Special Publication 811
National Institute of Standards and Technology · retrieved 2026-07-31
A national metrology institute's guidance on applying the SI, including symbol formatting. Authoritative for usage rules in the United States; it interprets the SI rather than defining it.
The International System of Units (SI), 9th edition
Bureau International des Poids et Mesures · retrieved 2026-07-31
The defining document for SI unit names and symbols, including the capitalisation and spacing rules. It defines units; it says nothing about how a symbol is encoded in a character set, and nothing about non-SI units except where it lists those accepted for use with the SI.

Last reviewed 2026-08-01