diff --git a/app/src/main/kotlin/com/simplemobiletools/calculator/activities/MainActivity.kt b/app/src/main/kotlin/com/simplemobiletools/calculator/activities/MainActivity.kt
index 007ac112..c363d6e4 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calculator/activities/MainActivity.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calculator/activities/MainActivity.kt
@@ -42,6 +42,10 @@ class MainActivity : SimpleActivity(), Calculator {
         btn_power.setOnClickListener { calc.handleOperation(POWER); checkHaptic(it) }
         btn_root.setOnClickListener { calc.handleOperation(ROOT); checkHaptic(it) }
 
+        btn_minus.setOnLongClickListener {
+            calc.turnToNegative()
+        }
+
         btn_clear.setOnClickListener { calc.handleClear(); checkHaptic(it) }
         btn_clear.setOnLongClickListener { calc.handleReset(); true }
 
diff --git a/app/src/main/kotlin/com/simplemobiletools/calculator/helpers/CalculatorImpl.kt b/app/src/main/kotlin/com/simplemobiletools/calculator/helpers/CalculatorImpl.kt
index 2029fcac..d611e1c0 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calculator/helpers/CalculatorImpl.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calculator/helpers/CalculatorImpl.kt
@@ -123,6 +123,25 @@ class CalculatorImpl(calculator: Calculator, private val context: Context) {
         showNewResult(inputDisplayedFormula)
     }
 
+    fun turnToNegative(): Boolean {
+        if (inputDisplayedFormula.isEmpty()) {
+            return false
+        }
+
+        if (!inputDisplayedFormula.trimStart('-').any { it.toString() in operations } && inputDisplayedFormula.replace(",", "").toDouble() != 0.0) {
+            inputDisplayedFormula = if (inputDisplayedFormula.first() == '-') {
+                inputDisplayedFormula.substring(1)
+            } else {
+                "-$inputDisplayedFormula"
+            }
+
+            showNewResult(inputDisplayedFormula)
+            return true
+        }
+
+        return false
+    }
+
     // handle percents manually, it doesn't seem to be possible via net.objecthunter:exp4j. "%" is used only for modulo there
     private fun handlePercent() {
         var result = calculatePercentage(baseValue, getSecondValue(), lastOperation)