diff --git a/examples/jspsych-html-button-response.html b/examples/jspsych-html-button-response.html
index 39bdeeaf35..99db2e3a4e 100644
--- a/examples/jspsych-html-button-response.html
+++ b/examples/jspsych-html-button-response.html
@@ -20,6 +20,7 @@
     type: jsPsychHtmlButtonResponse,
     stimulus: '<p style="color: red; font-size: 48px; font-weight: bold;">GREEN</p>',
     choices: ['Green', 'Blue', 'Red'],
+    button_layout: "flex",
     prompt: "<p>What color is this word? (flex layout)</p>"
   });
 
@@ -31,6 +32,15 @@
     prompt: "<p>What color is this word? (grid layout)</p>"
   });
 
+  timeline.push({
+    type: jsPsychHtmlButtonResponse,
+    stimulus: '<p style="color: red; font-size: 48px; font-weight: bold;">GREEN</p>',
+    choices: ['Green', 'Blue', 'Red'],
+    button_layout: "grid",
+    button_rows: 2,
+    prompt: "<p>What color is this word? (grid layout, two rows)</p>"
+  });
+
   timeline.push({
     type: jsPsychHtmlButtonResponse,
     stimulus: '<p style="color: green; font-size: 48px; font-weight: bold;">GREEN</p>',
diff --git a/packages/jspsych/src/index.scss b/packages/jspsych/src/index.scss
index 4093c9824c..4b6ab3ba4d 100644
--- a/packages/jspsych/src/index.scss
+++ b/packages/jspsych/src/index.scss
@@ -68,7 +68,9 @@
 .jspsych-btn-group-grid {
   display: grid;
   grid-auto-columns: max-content;
-  min-width: fit-content;
+  max-width: fit-content;
+  margin-right: auto;
+  margin-left: auto;
 }
 
 /* borrowing Bootstrap style for btn elements, but combining styles a bit */
diff --git a/packages/plugin-html-button-response/src/index.ts b/packages/plugin-html-button-response/src/index.ts
index 1ec684a3f7..1f5d61639b 100644
--- a/packages/plugin-html-button-response/src/index.ts
+++ b/packages/plugin-html-button-response/src/index.ts
@@ -51,19 +51,22 @@ const info = <const>{
       pretty_name: "Button layout",
       default: "grid",
     },
-    /** The number of grid rows when `button_layout` is "grid" */
+    /** The number of grid rows when `button_layout` is "grid".
+     * Setting to `null` will infer the number of rows based on the
+     * number of columns and buttons.
+     */
     button_rows: {
-      type: ParameterType.STRING,
+      type: ParameterType.INT,
       pretty_name: "Grid rows",
-      default: "1",
+      default: 1,
     },
     /** The number of grid columns when `button_layout` is "grid".
-     * Using "auto" will make the number of columns equal the number
-     * of buttons. */
+     * Setting to `null` (default value) will infer the number of columns
+     * based on the number of rows and buttons. */
     button_cols: {
-      type: ParameterType.STRING,
+      type: ParameterType.INT,
       pretty_name: "Grid columns",
-      default: "auto",
+      default: null,
     },
     /** If true, then trial will end when user responds. */
     response_ends_trial: {
@@ -100,10 +103,21 @@ class HtmlButtonResponsePlugin implements JsPsychPlugin<Info> {
     buttonGroupElement.id = "jspsych-html-button-response-btngroup";
     if (trial.button_layout === "grid") {
       buttonGroupElement.classList.add("jspsych-btn-group-grid");
-      let n_cols =
-        trial.button_cols === "auto" ? trial.choices.length : parseInt(trial.button_cols);
+      if (trial.button_rows === null && trial.button_cols === null) {
+        throw new Error(
+          "You must specify the number of rows or columns when using the grid layout."
+        );
+      }
+      const n_cols =
+        trial.button_cols === null
+          ? Math.ceil(trial.choices.length / trial.button_rows)
+          : trial.button_cols;
+      const n_rows =
+        trial.button_rows === null
+          ? Math.ceil(trial.choices.length / trial.button_cols)
+          : trial.button_rows;
       buttonGroupElement.style.gridTemplateColumns = `repeat(${n_cols}, 1fr)`;
-      buttonGroupElement.style.gridTemplateRows = `repeat(${trial.button_rows}, 1fr)`;
+      buttonGroupElement.style.gridTemplateRows = `repeat(${n_rows}, 1fr)`;
     } else if (trial.button_layout === "flex") {
       buttonGroupElement.classList.add("jspsych-btn-group-flex");
     }