diff --git a/Userland/Applications/Calculator/Keypad.cpp b/Userland/Applications/Calculator/Keypad.cpp
index 8881518769..48cd3568d0 100644
--- a/Userland/Applications/Calculator/Keypad.cpp
+++ b/Userland/Applications/Calculator/Keypad.cpp
@@ -19,6 +19,7 @@ Keypad::~Keypad()
 
 void Keypad::type_digit(int digit)
 {
+    u64 previous_value = 0;
     switch (m_state) {
     case State::External:
         m_state = State::TypingInteger;
@@ -28,17 +29,22 @@ void Keypad::type_digit(int digit)
         m_frac_length = 0;
         break;
     case State::TypingInteger:
-        VERIFY(m_frac_value == 0);
+        VERIFY(m_frac_value.value() == 0);
         VERIFY(m_frac_length == 0);
+        previous_value = m_int_value.value();
         m_int_value *= 10;
         m_int_value += digit;
+        if (m_int_value.has_overflow())
+            m_int_value = previous_value;
         break;
     case State::TypingDecimal:
-        if (m_frac_length > 6)
-            break;
+        previous_value = m_frac_value.value();
         m_frac_value *= 10;
         m_frac_value += digit;
-        m_frac_length++;
+        if (m_frac_value.has_overflow())
+            m_frac_value = previous_value;
+        else
+            m_frac_length++;
         break;
     }
 }
@@ -53,7 +59,7 @@ void Keypad::type_decimal_point()
         m_frac_length = 0;
         break;
     case State::TypingInteger:
-        VERIFY(m_frac_value == 0);
+        VERIFY(m_frac_value.value() == 0);
         VERIFY(m_frac_length == 0);
         m_state = State::TypingDecimal;
         break;
@@ -78,14 +84,14 @@ void Keypad::type_backspace()
             m_frac_length--;
             break;
         }
-        VERIFY(m_frac_value == 0);
+        VERIFY(m_frac_value.value() == 0);
         m_state = State::TypingInteger;
         [[fallthrough]];
     case State::TypingInteger:
-        VERIFY(m_frac_value == 0);
+        VERIFY(m_frac_value.value() == 0);
         VERIFY(m_frac_length == 0);
         m_int_value /= 10;
-        if (m_int_value == 0)
+        if (m_int_value.value() == 0)
             m_negative = false;
         break;
     }
@@ -95,15 +101,15 @@ double Keypad::value() const
 {
     double res = 0.0;
 
-    long frac = m_frac_value;
+    u64 frac = m_frac_value.value();
     for (int i = 0; i < m_frac_length; i++) {
-        int digit = frac % 10;
+        u8 digit = frac % 10;
         res += digit;
         res /= 10.0;
         frac /= 10;
     }
 
-    res += m_int_value;
+    res += m_int_value.value();
     if (m_negative)
         res = -res;
 
@@ -121,7 +127,7 @@ void Keypad::set_value(double value)
         m_negative = false;
 
     m_int_value = value;
-    value -= m_int_value;
+    value -= m_int_value.value();
 
     m_frac_value = 0;
     m_frac_length = 0;
@@ -143,7 +149,7 @@ String Keypad::to_string() const
     StringBuilder builder;
     if (m_negative)
         builder.append("-");
-    builder.appendff("{}", m_int_value);
+    builder.appendff("{}", m_int_value.value());
 
     // NOTE: This is so the decimal point appears on screen as soon as you type it.
     if (m_frac_length > 0 || m_state == State::TypingDecimal)
@@ -152,7 +158,7 @@ String Keypad::to_string() const
     if (m_frac_length > 0) {
         // FIXME: This disables the compiletime format string check since we can't parse '}}' here correctly.
         //        remove the 'StringView { }' when that's fixed.
-        builder.appendff(StringView { "{:0{}}" }, m_frac_value, m_frac_length);
+        builder.appendff(StringView { "{:0{}}" }, m_frac_value.value(), m_frac_length);
     }
 
     return builder.to_string();
diff --git a/Userland/Applications/Calculator/Keypad.h b/Userland/Applications/Calculator/Keypad.h
index 235a967b61..d090f6ff5c 100644
--- a/Userland/Applications/Calculator/Keypad.h
+++ b/Userland/Applications/Calculator/Keypad.h
@@ -30,9 +30,9 @@ public:
 private:
     // Internal representation of the current decimal value.
     bool m_negative { false };
-    long m_int_value { 0 };
-    long m_frac_value { 0 };
-    int m_frac_length { 0 };
+    Checked<u64> m_int_value { 0 };
+    Checked<u64> m_frac_value { 0 };
+    u8 m_frac_length { 0 };
     // E.g. for -35.004200,
     // m_negative = true
     // m_int_value = 35