diff --git a/src/pages/index.astro b/src/pages/index.astro
index 7ece35b..3d2cd87 100644
--- a/src/pages/index.astro
+++ b/src/pages/index.astro
@@ -85,6 +85,11 @@ const backendUrl = import.meta.env.PUBLIC_BACKEND_URL
           </p>
         </div>
         <input name='geolocation' id='geolocation-input' hidden />
+        <input
+          name='geolocation-diameter'
+          id='geolocation-diameter-input'
+          hidden
+        />
       </div>
 
       <div>
diff --git a/src/scripts/initSelectionMap.ts b/src/scripts/initSelectionMap.ts
index de73aef..bc24815 100644
--- a/src/scripts/initSelectionMap.ts
+++ b/src/scripts/initSelectionMap.ts
@@ -167,6 +167,10 @@ const DiameterControl = L.Control.extend({
       targetLocationCircle.setRadius(targetLocationCircleRadius)
 
       diameterText.innerText = `${targetLocationCircleRadius.toString()}m`
+      updateInputValue(
+        "geolocation-diameter-input",
+        targetLocationCircleRadius.toString()
+      )
       L.DomEvent.stop(ev)
     })
 
@@ -181,6 +185,10 @@ const DiameterControl = L.Control.extend({
       )
       targetLocationCircle.setRadius(targetLocationCircleRadius)
       diameterText.innerText = `${targetLocationCircleRadius.toString()}m`
+      updateInputValue(
+        "geolocation-diameter-input",
+        targetLocationCircleRadius.toString()
+      )
 
       L.DomEvent.stop(ev)
     })