diff --git a/README.md b/README.md
index a2779c3..31e7e84 100644
--- a/README.md
+++ b/README.md
@@ -84,6 +84,7 @@ round(sqrt(2)^4)! liters
 - Energy
 - Power
 - Pressure
+- Frequency
 - Speed
 - Temperature
 
@@ -179,7 +180,6 @@ Nice list of units: https://support.google.com/websearch/answer/3284611
 - Angles
 - Electric current, capacitance, charge, conductance, volts
 - Flow rate
-- Frequency
 
 ### Cross-compiling
 1. [Install Docker](https://docs.docker.com/get-docker/)
diff --git a/src/lexer.rs b/src/lexer.rs
index f519c3b..8ca3ecf 100644
--- a/src/lexer.rs
+++ b/src/lexer.rs
@@ -306,6 +306,14 @@ pub fn lex(input: &str, allow_trailing_operators: bool, default_degree: Unit) ->
             "psi" => tokens.push(Token::Unit(PoundsPerSquareInch)),
             "torr" | "torrs" => tokens.push(Token::Unit(Torr)),
 
+            "hz" | "hertz" => tokens.push(Token::Unit(Hertz)),
+            "khz" | "kilohertz" => tokens.push(Token::Unit(Kilohertz)),
+            "mhz" | "megahertz" => tokens.push(Token::Unit(Megahertz)),
+            "ghz" | "gigahertz" => tokens.push(Token::Unit(Gigahertz)),
+            "thz" | "terahertz" => tokens.push(Token::Unit(Terahertz)),
+            "phz" | "petahertz" => tokens.push(Token::Unit(Petahertz)),
+            "rpm" | "r/min" | "rev/min" => tokens.push(Token::Unit(RevolutionsPerMinute)),
+
             "kph" | "kmh" => tokens.push(Token::Unit(KilometersPerHour)),
             "mps" => tokens.push(Token::Unit(MetersPerSecond)),
             "mph" => tokens.push(Token::Unit(MilesPerHour)),
diff --git a/src/units.rs b/src/units.rs
index fec6bf0..343b977 100644
--- a/src/units.rs
+++ b/src/units.rs
@@ -25,6 +25,8 @@ pub enum UnitType {
   Power,
   /// A unit of pressure, for example `Bar`
   Pressure,
+  /// A unit of frequency, for example `Hertz`
+  Frequency,
   /// A unit of x, for example `KilometersPerHour`
   Speed,
   /// A unit of temperature, for example `Kelvin`
@@ -216,6 +218,14 @@ create_units!(
   PoundsPerSquareInch:          (Pressure, d128!(6894.757293168361)), // inexact
   Torr:                         (Pressure, d128!(162.12)),
 
+  Hertz:                        (Frequency, d128!(1)),
+  Kilohertz:                    (Frequency, d128!(1000)),
+  Megahertz:                    (Frequency, d128!(1000000)),
+  Gigahertz:                    (Frequency, d128!(1000000000)),
+  Terahertz:                    (Frequency, d128!(1000000000000)),
+  Petahertz:                    (Frequency, d128!(1000000000000000)),
+  RevolutionsPerMinute:         (Frequency, d128!(60)),
+
   KilometersPerHour:  (Speed, d128!(1)),
   MetersPerSecond:    (Speed, d128!(3.6)),
   MilesPerHour:       (Speed, d128!(1.609344)),