diff --git a/addons/addon-fit/src/FitAddon.ts b/addons/addon-fit/src/FitAddon.ts
index 2087e6146a..030fca4b41 100644
--- a/addons/addon-fit/src/FitAddon.ts
+++ b/addons/addon-fit/src/FitAddon.ts
@@ -31,8 +31,8 @@ export class FitAddon implements ITerminalAddon , IFitApi {
 
   public dispose(): void {}
 
-  public fit(): void {
-    const dims = this.proposeDimensions();
+  public fit(rect: object | undefined): void {
+    const dims = this.proposeDimensions(rect);
     if (!dims || !this._terminal || isNaN(dims.cols) || isNaN(dims.rows)) {
       return;
     }
@@ -47,7 +47,7 @@ export class FitAddon implements ITerminalAddon , IFitApi {
     }
   }
 
-  public proposeDimensions(): ITerminalDimensions | undefined {
+  public proposeDimensions(rect: object | undefined): ITerminalDimensions | undefined {
     if (!this._terminal) {
       return undefined;
     }
@@ -68,8 +68,8 @@ export class FitAddon implements ITerminalAddon , IFitApi {
       0 : core.viewport.scrollBarWidth;
 
     const parentElementStyle = window.getComputedStyle(this._terminal.element.parentElement);
-    const parentElementHeight = parseInt(parentElementStyle.getPropertyValue('height'));
-    const parentElementWidth = Math.max(0, parseInt(parentElementStyle.getPropertyValue('width')));
+    const parentElementHeight = (rect && rect.height) ? rect.height : parseInt(parentElementStyle.getPropertyValue('height'));
+    const parentElementWidth = (rect && rect.width) ? rect.width : Math.max(0, parseInt(parentElementStyle.getPropertyValue('width')));
     const elementStyle = window.getComputedStyle(this._terminal.element);
     const elementPadding = {
       top: parseInt(elementStyle.getPropertyValue('padding-top')),
diff --git a/addons/addon-fit/typings/addon-fit.d.ts b/addons/addon-fit/typings/addon-fit.d.ts
index e3d20e29f5..e5cfb34116 100644
--- a/addons/addon-fit/typings/addon-fit.d.ts
+++ b/addons/addon-fit/typings/addon-fit.d.ts
@@ -30,12 +30,12 @@ declare module '@xterm/addon-fit' {
     /**
      * Resizes the terminal to the dimensions of its containing element.
      */
-    public fit(): void;
+    public fit(rect: object): void;
 
     /**
      * Gets the proposed dimensions that will be used for a fit.
      */
-    public proposeDimensions(): ITerminalDimensions | undefined;
+    public proposeDimensions(rect: object): ITerminalDimensions | undefined;
   }
 
   /**