diff --git a/src/calculate.rs b/src/calculate.rs
index 3ebc697..e5c659e 100644
--- a/src/calculate.rs
+++ b/src/calculate.rs
@@ -980,7 +980,9 @@ fn calculate_right(number_string: (types::Value, types::Value)) -> types::Value
     let trimmed_string = match string {
         types::Value::Text(s) => {
             let temp: &'static str = Box::leak(s.into_boxed_str());
-            &temp[(temp.len() - trim_length)..]
+            let len = temp.len();
+            let start = if trim_length > len { len } else { trim_length };
+            &temp[(len - start)..]
         }
         _ => "",
     };
@@ -997,7 +999,9 @@ fn calculate_left(number_string: (types::Value, types::Value)) -> types::Value {
     let trimmed_string = match string {
         types::Value::Text(s) => {
             let temp: &'static str = Box::leak(s.into_boxed_str());
-            &temp[..trim_length]
+            let len = temp.len();
+            let end = if trim_length > len { len } else { trim_length };
+            &temp[..end]
         }
         _ => "",
     };
diff --git a/tests/test.rs b/tests/test.rs
index ac2c946..3120e1d 100644
--- a/tests/test.rs
+++ b/tests/test.rs
@@ -779,6 +779,9 @@ fn it_evaluate_left_and_right_functions() {
     assert_eq!(evaluate_formula_string("=LEFT(\"apple\")"), "a",);
 
     assert_eq!(evaluate_formula_string("=\"P\"&LEFT(\"000\"&1,3)"), "P000",);
+
+    assert_eq!(evaluate_formula_string("=LEFT(\"apple\", 10)"), "apple",);
+    assert_eq!(evaluate_formula_string("=RIGHT(\"apple\", 10)"), "apple",);
 }
 
 #[test]