diff --git a/generators/builtins/common.kt b/generators/builtins/common.kt
index b92994b7d90..19e720f37ab 100644
--- a/generators/builtins/common.kt
+++ b/generators/builtins/common.kt
@@ -44,6 +44,9 @@ enum class UnsignedType {
 
     val capitalized: String get() = name.substring(0, 2) + name.substring(2).toLowerCase()
     val asSigned: PrimitiveType = PrimitiveType.valueOf(name.substring(1))
+
+    val byteSize = (1 shl ordinal)
+    val mask = "0x${List(byteSize) { "FF" }.chunked(2).joinToString("_") { it.joinToString("") }}"
 }
 
 enum class ProgressionKind {
diff --git a/generators/builtins/unsignedTypes.kt b/generators/builtins/unsignedTypes.kt
index 8cf3a504975..43342dec271 100644
--- a/generators/builtins/unsignedTypes.kt
+++ b/generators/builtins/unsignedTypes.kt
@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.generators.builtins.unsigned
 
 
 import org.jetbrains.kotlin.generators.builtins.UnsignedType
+import org.jetbrains.kotlin.generators.builtins.convert
 import org.jetbrains.kotlin.generators.builtins.generateBuiltIns.BuiltInsSourceGenerator
 import org.jetbrains.kotlin.generators.builtins.ranges.GeneratePrimitives
 import java.io.File
@@ -160,13 +161,19 @@ class UnsignedTypeGenerator(val type: UnsignedType, out: PrintWriter) : BuiltIns
     private fun generateMemberConversions() {
         for (otherType in UnsignedType.values()) {
             val signed = otherType.asSigned.capitalized
-            out.println("    public fun to$signed(): $signed = TODO()")
+            out.print("    public fun to$signed(): $signed = ")
+            out.println(when {
+                otherType < type -> "data.to$signed()"
+                otherType == type -> "data"
+                else -> "data.to$signed() and ${type.mask}"
+            })
         }
         out.println()
 
         for (otherType in UnsignedType.values()) {
             val name = otherType.capitalized
-            out.println("    public fun to$name(): $name = TODO()")
+            out.print("    public fun to$name(): $name = ")
+            out.println(if (type == otherType) "this" else "data.to${otherType.capitalized}()")
         }
         out.println()
     }
@@ -175,7 +182,12 @@ class UnsignedTypeGenerator(val type: UnsignedType, out: PrintWriter) : BuiltIns
         for (otherType in UnsignedType.values()) {
             val otherSigned = otherType.asSigned.capitalized
             val thisSigned = type.asSigned.capitalized
-            out.println("public fun $otherSigned.to$className(): $className = $className(this.to$thisSigned())")
+            out.print("public fun $otherSigned.to$className(): $className = ")
+            out.println(when {
+                otherType < type -> "$className(this.to$thisSigned() and ${otherType.mask})"
+                otherType == type -> "$className(this)"
+                else -> "$className(this.to$thisSigned())"
+            })
         }
     }
 
diff --git a/libraries/stdlib/unsigned/src/kotlin/UByte.kt b/libraries/stdlib/unsigned/src/kotlin/UByte.kt
index e8988f8b43c..31a0797a16c 100644
--- a/libraries/stdlib/unsigned/src/kotlin/UByte.kt
+++ b/libraries/stdlib/unsigned/src/kotlin/UByte.kt
@@ -113,19 +113,19 @@ public inline class UByte internal constructor(private val data: Byte) : Compara
     /** Inverts the bits in this value. */
     public fun inv(): UByte = UByte(data.inv())
 
-    public fun toByte(): Byte = TODO()
-    public fun toShort(): Short = TODO()
-    public fun toInt(): Int = TODO()
-    public fun toLong(): Long = TODO()
+    public fun toByte(): Byte = data
+    public fun toShort(): Short = data.toShort() and 0xFF
+    public fun toInt(): Int = data.toInt() and 0xFF
+    public fun toLong(): Long = data.toLong() and 0xFF
 
-    public fun toUByte(): UByte = TODO()
-    public fun toUShort(): UShort = TODO()
-    public fun toUInt(): UInt = TODO()
-    public fun toULong(): ULong = TODO()
+    public fun toUByte(): UByte = this
+    public fun toUShort(): UShort = data.toUShort()
+    public fun toUInt(): UInt = data.toUInt()
+    public fun toULong(): ULong = data.toULong()
 
 }
 
-public fun Byte.toUByte(): UByte = UByte(this.toByte())
+public fun Byte.toUByte(): UByte = UByte(this)
 public fun Short.toUByte(): UByte = UByte(this.toByte())
 public fun Int.toUByte(): UByte = UByte(this.toByte())
 public fun Long.toUByte(): UByte = UByte(this.toByte())
diff --git a/libraries/stdlib/unsigned/src/kotlin/UInt.kt b/libraries/stdlib/unsigned/src/kotlin/UInt.kt
index bf5780aeafa..3cb5e5d1cfa 100644
--- a/libraries/stdlib/unsigned/src/kotlin/UInt.kt
+++ b/libraries/stdlib/unsigned/src/kotlin/UInt.kt
@@ -117,19 +117,19 @@ public inline class UInt internal constructor(private val data: Int) : Comparabl
     /** Inverts the bits in this value. */
     public fun inv(): UInt = UInt(data.inv())
 
-    public fun toByte(): Byte = TODO()
-    public fun toShort(): Short = TODO()
-    public fun toInt(): Int = TODO()
-    public fun toLong(): Long = TODO()
+    public fun toByte(): Byte = data.toByte()
+    public fun toShort(): Short = data.toShort()
+    public fun toInt(): Int = data
+    public fun toLong(): Long = data.toLong() and 0xFFFF_FFFF
 
-    public fun toUByte(): UByte = TODO()
-    public fun toUShort(): UShort = TODO()
-    public fun toUInt(): UInt = TODO()
-    public fun toULong(): ULong = TODO()
+    public fun toUByte(): UByte = data.toUByte()
+    public fun toUShort(): UShort = data.toUShort()
+    public fun toUInt(): UInt = this
+    public fun toULong(): ULong = data.toULong()
 
 }
 
-public fun Byte.toUInt(): UInt = UInt(this.toInt())
-public fun Short.toUInt(): UInt = UInt(this.toInt())
-public fun Int.toUInt(): UInt = UInt(this.toInt())
+public fun Byte.toUInt(): UInt = UInt(this.toInt() and 0xFF)
+public fun Short.toUInt(): UInt = UInt(this.toInt() and 0xFFFF)
+public fun Int.toUInt(): UInt = UInt(this)
 public fun Long.toUInt(): UInt = UInt(this.toInt())
diff --git a/libraries/stdlib/unsigned/src/kotlin/ULong.kt b/libraries/stdlib/unsigned/src/kotlin/ULong.kt
index 6fdee736deb..81628fead6e 100644
--- a/libraries/stdlib/unsigned/src/kotlin/ULong.kt
+++ b/libraries/stdlib/unsigned/src/kotlin/ULong.kt
@@ -117,19 +117,19 @@ public inline class ULong internal constructor(private val data: Long) : Compara
     /** Inverts the bits in this value. */
     public fun inv(): ULong = ULong(data.inv())
 
-    public fun toByte(): Byte = TODO()
-    public fun toShort(): Short = TODO()
-    public fun toInt(): Int = TODO()
-    public fun toLong(): Long = TODO()
+    public fun toByte(): Byte = data.toByte()
+    public fun toShort(): Short = data.toShort()
+    public fun toInt(): Int = data.toInt()
+    public fun toLong(): Long = data
 
-    public fun toUByte(): UByte = TODO()
-    public fun toUShort(): UShort = TODO()
-    public fun toUInt(): UInt = TODO()
-    public fun toULong(): ULong = TODO()
+    public fun toUByte(): UByte = data.toUByte()
+    public fun toUShort(): UShort = data.toUShort()
+    public fun toUInt(): UInt = data.toUInt()
+    public fun toULong(): ULong = this
 
 }
 
-public fun Byte.toULong(): ULong = ULong(this.toLong())
-public fun Short.toULong(): ULong = ULong(this.toLong())
-public fun Int.toULong(): ULong = ULong(this.toLong())
-public fun Long.toULong(): ULong = ULong(this.toLong())
+public fun Byte.toULong(): ULong = ULong(this.toLong() and 0xFF)
+public fun Short.toULong(): ULong = ULong(this.toLong() and 0xFFFF)
+public fun Int.toULong(): ULong = ULong(this.toLong() and 0xFFFF_FFFF)
+public fun Long.toULong(): ULong = ULong(this)
diff --git a/libraries/stdlib/unsigned/src/kotlin/UShort.kt b/libraries/stdlib/unsigned/src/kotlin/UShort.kt
index ef9609da2cc..e881611285c 100644
--- a/libraries/stdlib/unsigned/src/kotlin/UShort.kt
+++ b/libraries/stdlib/unsigned/src/kotlin/UShort.kt
@@ -113,19 +113,19 @@ public inline class UShort internal constructor(private val data: Short) : Compa
     /** Inverts the bits in this value. */
     public fun inv(): UShort = UShort(data.inv())
 
-    public fun toByte(): Byte = TODO()
-    public fun toShort(): Short = TODO()
-    public fun toInt(): Int = TODO()
-    public fun toLong(): Long = TODO()
+    public fun toByte(): Byte = data.toByte()
+    public fun toShort(): Short = data
+    public fun toInt(): Int = data.toInt() and 0xFFFF
+    public fun toLong(): Long = data.toLong() and 0xFFFF
 
-    public fun toUByte(): UByte = TODO()
-    public fun toUShort(): UShort = TODO()
-    public fun toUInt(): UInt = TODO()
-    public fun toULong(): ULong = TODO()
+    public fun toUByte(): UByte = data.toUByte()
+    public fun toUShort(): UShort = this
+    public fun toUInt(): UInt = data.toUInt()
+    public fun toULong(): ULong = data.toULong()
 
 }
 
-public fun Byte.toUShort(): UShort = UShort(this.toShort())
-public fun Short.toUShort(): UShort = UShort(this.toShort())
+public fun Byte.toUShort(): UShort = UShort(this.toShort() and 0xFF)
+public fun Short.toUShort(): UShort = UShort(this)
 public fun Int.toUShort(): UShort = UShort(this.toShort())
 public fun Long.toUShort(): UShort = UShort(this.toShort())