diff --git a/src/nodes/from_str.rs b/src/nodes/from_str.rs
index 4f0f20d..f4b147d 100644
--- a/src/nodes/from_str.rs
+++ b/src/nodes/from_str.rs
@@ -9,6 +9,7 @@ impl Node {
         Ok(match s {
             "c" => Self::Number(Float::with_val(PREC, 299_792_458)),
             "A" => Self::Number(Float::with_val(PREC, 6.02214076e23)),
+            "pi" => Self::Number(Float::with_val(PREC, 3.1415926536)),
             _ => Self::Function(s.parse()?),
         })
     }
diff --git a/src/nodes/tests.rs b/src/nodes/tests.rs
index 59995fe..81c2ab9 100644
--- a/src/nodes/tests.rs
+++ b/src/nodes/tests.rs
@@ -22,6 +22,10 @@ fn constants() {
         Nodes::from_str("A").unwrap().evaluate().to_f64(),
         6.02214076e23
     );
+    assert_eq!(
+        Nodes::from_str("pi").unwrap().evaluate().to_f64(),
+        3.1415926536
+    );
 }
 
 #[test]