diff --git a/src/editor/block/math.js b/src/editor/block/math.js
index aff548d..e7cf9b2 100644
--- a/src/editor/block/math.js
+++ b/src/editor/block/math.js
@@ -67,10 +67,19 @@ function mathDeco(view) {
 
                 // if we got a result from math.js, add the result decoration
                 if (result !== undefined) {
+                    let format = parser.get("format")
+
                     let resultWidget
                     if (typeof(result) === "string") {
                         resultWidget = new MathResult(result, result)
-                    } else {
+                    } else if (format !== undefined && typeof(format) === "function") {
+                        try {
+                            resultWidget = new MathResult(format(result), format(result))
+                        } catch (e) {
+                            // suppress any errors
+                        }
+                    }
+                    if (resultWidget === undefined) {
                         resultWidget = new MathResult(
                             math.format(result, {
                                 precision: 8,
diff --git a/tests/math.spec.js b/tests/math.spec.js
index 7c04d11..d6913e5 100644
--- a/tests/math.spec.js
+++ b/tests/math.spec.js
@@ -24,3 +24,13 @@ format(1/3, 3)
 `)
         await expect(page.locator("css=.heynote-math-result")).toHaveText("0.333")
 })
+
+test("custom format function", async ({ page }) => {
+    await heynotePage.setContent(`
+∞∞∞math
+_format = format
+format(x) = _format(x, {notation:"exponential"})
+42
+`)
+    await expect(page.locator("css=.heynote-math-result").last()).toHaveText("4.2e+1")
+})