diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6981dc0..5cfb121 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,6 @@
 # Changelog
 
-## Next
+## 4.0.0 - 2026 Jun 27
 - Rewrite units to be exponent-based, making things like `km^5` and `sqkm^-1` possible
 - Add generic unit multiplication and division, such as `1kg/1m` and `1m*1kg`
 - Add generic unit combinations, such as `1kg/m`, `1km per year` and `m+km`
@@ -10,7 +10,7 @@
 - Use max precision for inexact unit conversions
 - Fix `^` allowing numbers to be raised to the power of units
 
-## 3.1.0 - 2025 Jun 20
+## 3.1.0 - 2026 Jun 20
 - Add FLOP and FLOPS units
 - Update `fastnum` dependency
 - Fix conversion of `torr`, `btu/s` and `btu/h`
diff --git a/Cargo.lock b/Cargo.lock
index adc5e9f..1c8dba7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -47,7 +47,7 @@ dependencies = [
 
 [[package]]
 name = "cpc"
-version = "3.1.0"
+version = "4.0.0"
 dependencies = [
  "console_error_panic_hook",
  "fastnum",
diff --git a/Cargo.toml b/Cargo.toml
index 2e089a6..3a9ec9f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "cpc"
-version = "3.1.0"
+version = "4.0.0"
 description = "evaluates math expressions, with support for units and conversion between units"
 authors = ["Kasper Henningsen"]
 edition = "2024"