diff --git a/board/static/board/post.js b/board/static/board/post.js
index a19bd3e..391ad5e 100644
--- a/board/static/board/post.js
+++ b/board/static/board/post.js
@@ -73,10 +73,11 @@ function openReplyWindow(replyUrl) {
         return getReplyWindow();
     }
 
+    let width = Math.min(window.top.innerWidth - 20, 500);
     let replyWindow = window.top.jsFrame.create({
         title: "New Reply",
         name: replyWindowName,
-        width: 500,
+        width: width,
         url: replyUrl
     });
     $(replyWindow.iframe, "iframe").on("load", () => {
@@ -123,10 +124,11 @@ function openPostWindow(postUrl) {
     if (window.top.jsFrame.containsWindowName(postWindowName)) {
         return;
     }
+    let width = Math.min(window.top.innerWidth - 20, 500);
     let postWindow = window.top.jsFrame.create({
         title: "New Thread",
         name: postWindowName,
-        width: 500,
+        width: width,
         url: postUrl,
     });
     $(postWindow.iframe, "iframe").on("load", () => {
@@ -153,10 +155,11 @@ function openReportWindow(reportUrl) {
     if (window.top.jsFrame.containsWindowName(reportWindowName)) {
         getReportWindow().closeFrame();
     }
+    let width = Math.min(window.top.innerWidth - 20, 360);
     let reportWindow = window.top.jsFrame.create({
         url: reportUrl,
         name: reportWindowName,
-        width: 360,
+        width: width,
     });
     $(reportWindow.iframe, "iframe").on("load", () => {
         fitWindowToContent(reportWindow);