diff --git a/lib/tick.ts b/lib/tick.ts
index 9a2161a..a4b8c2b 100644
--- a/lib/tick.ts
+++ b/lib/tick.ts
@@ -19,7 +19,7 @@ export function tick(fps: number): Source<PhysicsTick | RenderTick> {
 
       let animationFrame = requestAnimationFrame(function animationTick() {
         const now = new Date().getTime();
-        callback(["render", now - lastPhysicsTick]);
+        callback(["render", (now - lastPhysicsTick) / 1000]);
         animationFrame = requestAnimationFrame(animationTick);
       });