diff --git a/projects/tip-calculator/index.js b/projects/tip-calculator/index.js
index 98cb079..35facbb 100644
--- a/projects/tip-calculator/index.js
+++ b/projects/tip-calculator/index.js
@@ -6,8 +6,12 @@ const totalSpan = document.getElementById("total");
 function calculateTotal() {
   const billValue = billInput.value;
   const tipValue = tipInput.value;
+  if(tipValue<=0||billValue<=0){
+    alert("bill value or tip value cannot be less than equal to zero);
+  }else{
   const totalValue = billValue * (1 + tipValue / 100);
   totalSpan.innerText = totalValue.toFixed(2);
+  }
 }
 
 btnEl.addEventListener("click", calculateTotal);