diff --git a/src/routes/+page.svelte b/src/routes/+page.svelte
index 72e67c7..e4ab9b7 100644
--- a/src/routes/+page.svelte
+++ b/src/routes/+page.svelte
@@ -86,9 +86,9 @@
         return volume;
     })
 
-    let maxWeight = derived(totalThrust / (gravity * 9.81))
+    let maxWeight = $derived(totalThrust / (gravity * 9.81))
 
-    let maxCargoWeight = $derived(maxWeight -= totalVolume * weightPerVolume)
+    let maxCargoWeight = $derived(maxWeight - totalVolume * weightPerVolume)
 
     function weightConversion(weight: number): string {
         if (weight > 1000) {