--- a/crates/jrsonnet-stdlib/src/lib.rs
+++ b/crates/jrsonnet-stdlib/src/lib.rs
@@ -86,6 +86,7 @@
 		("sign", builtin_sign::INST),
 		("max", builtin_max::INST),
 		("min", builtin_min::INST),
+		("sum", builtin_sum::INST),
 		("modulo", builtin_modulo::INST),
 		("floor", builtin_floor::INST),
 		("ceil", builtin_ceil::INST),
--- a/crates/jrsonnet-stdlib/src/math.rs
+++ b/crates/jrsonnet-stdlib/src/math.rs
@@ -25,6 +25,11 @@
 }
 
 #[builtin]
+pub fn builtin_sum(arr: Vec<f64>) -> f64 {
+	arr.iter().sum()
+}
+
+#[builtin]
 pub fn builtin_modulo(x: f64, y: f64) -> f64 {
 	x % y
 }