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---
title: <frequency-percentage>
slug: Web/CSS/frequency-percentage
page-type: css-type
browser-compat: css.types.frequency-percentage
---
{{CSSRef}}
The **`<frequency-percentage>`** [CSS](/en-US/docs/Web/CSS) [data type](/en-US/docs/Web/CSS/CSS_Types) represents a value that can be either a {{Cssxref("frequency")}} or a {{Cssxref("percentage")}}. Frequency values, e.g. the pitch of a speaking voice, are not currently used in any CSS properties.
## Syntax
The value of a `<frequency-percentage>` is either a {{Cssxref("frequency")}} or a {{Cssxref("percentage")}}; see their individual reference pages for details about their syntaxes.
## Description
### Use in calc()
Where a `<frequency-percentage>` is specified as an allowable type, this means that the percentage resolves to a frequency and therefore can be used in a [`calc()`](/en-US/docs/Web/CSS/calc) expression.
## Formal syntax
{{csssyntax}}
## Examples
### Valid percentage values
```plain example-good
90% Positive percentage
+90% Positive percentage with leading +
-90% Negative percentage — not valid for all properties that use percentages
```
### Invalid percentage values
```plain example-bad
90 % No space is allowed between the number and the unit
```
### Valid frequency values
```plain example-good
12Hz Positive integer
4.3Hz Non-integer
14KhZ The unit is case-insensitive, though non-SI capitalization is not recommended.
+0Hz Zero, with a leading + and a unit
-0kHz Zero, with a leading - and a unit
```
### Invalid frequency values
```plain example-bad
12.0 This is a <number>, not an <frequency>, because it is missing a unit.
7 Hz No space is allowed between the number and the unit.
0 Although unitless zero is an allowable <length>, it's an invalid <frequency>.
```
## Specifications
{{Specifications}}
## Browser compatibility
{{Compat}}
## See also
- [CSS data types](/en-US/docs/Web/CSS/CSS_Types)
- [CSS Values and Units](/en-US/docs/Web/CSS/CSS_Values_and_Units)
- Related CSS data types:
- {{cssxref("frequency", "<frequency>")}}
- {{cssxref("percentage", "<percentage>")}}