Hertz symbol

The two letters Hz, the SI unit symbol for the hertz.

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Meanings

Hz is the SI symbol for the hertz, one cycle per second. It is the unit on every radio dial, processor specification and mains-supply rating.

Officially standardisedVerified fact
Denotes the hertz, the SI derived unit of frequency, equal to one cycle per second.
Contexts: Mathematics
Officially standardisedVerified fact
Is written with a capital H and a lower-case z, because the unit is named after Heinrich Hertz and only the first letter of an eponymous symbol is capitalised.
Contexts: Mathematics
Common modern usageVerified fact
Appears with prefixes far more often than alone — kHz on a radio dial, MHz and GHz on processor and wireless specifications, and 50 or 60 Hz as a mains-supply frequency.
Contexts: Electrical equipment

Visual description

A capital Latin H — two vertical strokes joined by a horizontal crossbar — followed by a lower-case z, a zigzag of two horizontals joined by a diagonal.

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

SI base units
Bureau International des Poids et Mesures · retrieved 2026-07-31
The seven base units and their symbols as published by the defining body. A summary page: the SI Brochure remains the full instrument.
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.
SI derived unit
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

Hz is the SI symbol for the hertz, one cycle per second. It is the unit on every radio dial, processor specification and mains-supply rating.

Officially standardisedVerified fact

Denotes the hertz, the SI derived unit of frequency, equal to one cycle per second.

Contexts: Mathematics

Officially standardisedVerified fact

Is written with a capital H and a lower-case z, because the unit is named after Heinrich Hertz and only the first letter of an eponymous symbol is capitalised.

Contexts: Mathematics

Common modern usageVerified fact

Appears with prefixes far more often than alone — kHz on a radio dial, MHz and GHz on processor and wireless specifications, and 50 or 60 Hz as a mains-supply frequency.

Contexts: Electrical equipment

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

SI base units
Bureau International des Poids et Mesures · retrieved 2026-07-31
The seven base units and their symbols as published by the defining body. A summary page: the SI Brochure remains the full instrument.
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.
SI derived unit
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