diff --git a/.changeset/smooth-taxis-mate.md b/.changeset/smooth-taxis-mate.md
new file mode 100644
index 0000000000..10221029c8
--- /dev/null
+++ b/.changeset/smooth-taxis-mate.md
@@ -0,0 +1,5 @@
+---
+"@khanacademy/perseus": patch
+---
+
+Internal: convert backgroundImage dimensions to numbers during parsing.
diff --git a/packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/string-to-number.test.ts b/packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/string-to-number.test.ts
new file mode 100644
index 0000000000..bb75d46206
--- /dev/null
+++ b/packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/string-to-number.test.ts
@@ -0,0 +1,40 @@
+import {success} from "../result";
+
+import {stringToNumber} from "./string-to-number";
+import {ctx, parseFailureWith} from "./test-helpers";
+
+describe("stringToNumber", () => {
+    it("accepts a number", () => {
+        expect(stringToNumber(42, ctx())).toEqual(success(42));
+    });
+
+    it("accepts a numeric string", () => {
+        expect(stringToNumber("7", ctx())).toEqual(success(7));
+    });
+
+    it("parses a decimal", () => {
+        expect(stringToNumber("5.5", ctx())).toEqual(success(5.5));
+    });
+
+    it("parses a negative number", () => {
+        expect(stringToNumber("-2", ctx())).toEqual(success(-2));
+    });
+
+    it("rejects the empty string", () => {
+        expect(stringToNumber("", ctx())).toEqual(
+            parseFailureWith({
+                badValue: "",
+                expected: ["a number or numeric string"],
+            }),
+        );
+    });
+
+    it("rejects a non-numeric string", () => {
+        expect(stringToNumber("3a", ctx())).toEqual(
+            parseFailureWith({
+                badValue: "3a",
+                expected: ["a number or numeric string"],
+            }),
+        );
+    });
+});
diff --git a/packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/string-to-number.ts b/packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/string-to-number.ts
new file mode 100644
index 0000000000..0569035c4f
--- /dev/null
+++ b/packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/string-to-number.ts
@@ -0,0 +1,17 @@
+import type {PartialParser} from "../parser-types";
+
+export const stringToNumber: PartialParser<string | number, number> = (
+    rawValue,
+    ctx,
+) => {
+    if (typeof rawValue === "number") {
+        return ctx.success(rawValue);
+    }
+
+    const parsedNumber = +rawValue;
+    if (rawValue === "" || isNaN(parsedNumber)) {
+        return ctx.failure("a number or numeric string", rawValue);
+    }
+
+    return ctx.success(parsedNumber);
+};
diff --git a/packages/perseus/src/util/parse-perseus-json/perseus-parsers/perseus-image-background.ts b/packages/perseus/src/util/parse-perseus-json/perseus-parsers/perseus-image-background.ts
index ae8c21b164..248644ce53 100644
--- a/packages/perseus/src/util/parse-perseus-json/perseus-parsers/perseus-image-background.ts
+++ b/packages/perseus/src/util/parse-perseus-json/perseus-parsers/perseus-image-background.ts
@@ -3,21 +3,26 @@ import {
     number,
     object,
     optional,
+    pipeParsers,
     string,
     union,
 } from "../general-purpose-parsers";
+import {stringToNumber} from "../general-purpose-parsers/string-to-number";
 
 import type {Parser} from "../parser-types";
 import type {PerseusImageBackground} from "@khanacademy/perseus";
 
+const numericToNumber = pipeParsers(union(number).or(string).parser).then(
+    stringToNumber,
+).parser;
+
 export const parsePerseusImageBackground: Parser<PerseusImageBackground> =
     object({
         url: optional(nullable(string)),
-        width: optional(number),
-        height: optional(number),
-        top: optional(number),
-        left: optional(number),
-        bottom: optional(number),
-        // TODO(benchristel): convert scale to a number
-        scale: optional(union(number).or(string).parser),
+        width: optional(numericToNumber),
+        height: optional(numericToNumber),
+        top: optional(numericToNumber),
+        left: optional(numericToNumber),
+        bottom: optional(numericToNumber),
+        scale: optional(numericToNumber),
     });
diff --git a/packages/perseus/src/util/parse-perseus-json/regression-tests/__snapshots__/parse-perseus-json-snapshot.test.ts.snap b/packages/perseus/src/util/parse-perseus-json/regression-tests/__snapshots__/parse-perseus-json-snapshot.test.ts.snap
index 1aa0ec1b21..a5b884de44 100644
--- a/packages/perseus/src/util/parse-perseus-json/regression-tests/__snapshots__/parse-perseus-json-snapshot.test.ts.snap
+++ b/packages/perseus/src/util/parse-perseus-json/regression-tests/__snapshots__/parse-perseus-json-snapshot.test.ts.snap
@@ -473,6 +473,166 @@ exports[`parseAndTypecheckPerseusItem correctly parses data/iframe-missing-stati
 }
 `;
 
+exports[`parseAndTypecheckPerseusItem correctly parses data/interactive-graph-with-string-backgroundImage-left.json 1`] = `
+{
+  "answer": undefined,
+  "answerArea": {
+    "calculator": false,
+    "chi2Table": false,
+    "periodicTable": false,
+    "tTable": false,
+    "zTable": false,
+  },
+  "hints": [],
+  "itemDataVersion": {
+    "major": 0,
+    "minor": 1,
+  },
+  "question": {
+    "content": "Ally is excited to compete in a $6$-mile race. The race organizers plotted the course on a coordinate map. The starting point is at $(4,3)$, and the ending point is at $(4,9)$.  Ally's family decides to stand at $(4,6)$ on the map.
+
+**Plot the starting point, ending point, and place where Ally's family stands on the map.**
+
+[[☃ interactive-graph 1]]
+
+**How far along will Ally be in the race when she reaches her family?**  
+[[☃ radio 1]]",
+    "images": {},
+    "metadata": undefined,
+    "widgets": {
+      "interactive-graph 1": {
+        "alignment": "default",
+        "graded": true,
+        "key": undefined,
+        "options": {
+          "backgroundImage": {
+            "bottom": 4,
+            "height": 0,
+            "left": 0,
+            "scale": 1,
+            "top": undefined,
+            "url": "",
+            "width": 0,
+          },
+          "correct": {
+            "coord": undefined,
+            "coords": [
+              [
+                4,
+                3,
+              ],
+              [
+                4,
+                6,
+              ],
+              [
+                4,
+                9,
+              ],
+            ],
+            "numPoints": 3,
+            "startCoords": undefined,
+            "type": "point",
+          },
+          "fullGraphAriaDescription": undefined,
+          "fullGraphLabel": undefined,
+          "graph": {
+            "coord": undefined,
+            "coords": undefined,
+            "numPoints": 3,
+            "startCoords": undefined,
+            "type": "point",
+          },
+          "gridStep": [
+            1,
+            1,
+          ],
+          "labels": [
+            "x",
+            "y",
+          ],
+          "lockedFigures": undefined,
+          "markings": "graph",
+          "range": [
+            [
+              -1,
+              10,
+            ],
+            [
+              -1,
+              10,
+            ],
+          ],
+          "rulerLabel": "",
+          "rulerTicks": 10,
+          "showProtractor": false,
+          "showRuler": false,
+          "showTooltips": false,
+          "snapStep": [
+            0.5,
+            0.5,
+          ],
+          "step": [
+            1,
+            1,
+          ],
+        },
+        "static": false,
+        "type": "interactive-graph",
+        "version": {
+          "major": 0,
+          "minor": 0,
+        },
+      },
+      "radio 1": {
+        "alignment": "default",
+        "graded": true,
+        "key": undefined,
+        "options": {
+          "choices": [
+            {
+              "clue": undefined,
+              "content": "Less than halfway through the race",
+              "correct": false,
+              "isNoneOfTheAbove": undefined,
+              "widgets": undefined,
+            },
+            {
+              "clue": undefined,
+              "content": "Halfway through the race",
+              "correct": true,
+              "isNoneOfTheAbove": undefined,
+              "widgets": undefined,
+            },
+            {
+              "clue": undefined,
+              "content": "More than halfway through the race",
+              "correct": undefined,
+              "isNoneOfTheAbove": undefined,
+              "widgets": undefined,
+            },
+          ],
+          "countChoices": false,
+          "deselectEnabled": false,
+          "displayCount": null,
+          "hasNoneOfTheAbove": false,
+          "multipleSelect": false,
+          "noneOfTheAbove": undefined,
+          "onePerLine": undefined,
+          "randomize": false,
+        },
+        "static": false,
+        "type": "radio",
+        "version": {
+          "major": 1,
+          "minor": 0,
+        },
+      },
+    },
+  },
+}
+`;
+
 exports[`parseAndTypecheckPerseusItem correctly parses data/item-missing-answerArea.json 1`] = `
 {
   "_multi": {
diff --git a/packages/perseus/src/util/parse-perseus-json/regression-tests/data/interactive-graph-with-string-backgroundImage-left.json b/packages/perseus/src/util/parse-perseus-json/regression-tests/data/interactive-graph-with-string-backgroundImage-left.json
new file mode 100644
index 0000000000..5e348cd967
--- /dev/null
+++ b/packages/perseus/src/util/parse-perseus-json/regression-tests/data/interactive-graph-with-string-backgroundImage-left.json
@@ -0,0 +1,125 @@
+{
+  "question": {
+    "content": "Ally is excited to compete in a $6$-mile race. The race organizers plotted the course on a coordinate map. The starting point is at $(4,3)$, and the ending point is at $(4,9)$.  Ally's family decides to stand at $(4,6)$ on the map.\n\n**Plot the starting point, ending point, and place where Ally's family stands on the map.**\n\n[[☃ interactive-graph 1]]\n\n**How far along will Ally be in the race when she reaches her family?**  \n[[☃ radio 1]]",
+    "images": {},
+    "widgets": {
+      "interactive-graph 1": {
+        "type": "interactive-graph",
+        "alignment": "default",
+        "static": false,
+        "graded": true,
+        "options": {
+          "step": [
+            1,
+            1
+          ],
+          "backgroundImage": {
+            "url": "",
+            "scale": "1",
+            "bottom": "4",
+            "left": "0",
+            "width": 0,
+            "height": 0
+          },
+          "markings": "graph",
+          "labels": [
+            "x",
+            "y"
+          ],
+          "showProtractor": false,
+          "showRuler": false,
+          "showTooltips": false,
+          "rulerLabel": "",
+          "rulerTicks": 10,
+          "range": [
+            [
+              -1,
+              10
+            ],
+            [
+              -1,
+              10
+            ]
+          ],
+          "gridStep": [
+            1,
+            1
+          ],
+          "snapStep": [
+            0.5,
+            0.5
+          ],
+          "graph": {
+            "type": "point",
+            "numPoints": 3
+          },
+          "correct": {
+            "type": "point",
+            "coords": [
+              [
+                4,
+                3
+              ],
+              [
+                4,
+                6
+              ],
+              [
+                4,
+                9
+              ]
+            ],
+            "numPoints": 3
+          }
+        },
+        "version": {
+          "major": 0,
+          "minor": 0
+        }
+      },
+      "radio 1": {
+        "type": "radio",
+        "alignment": "default",
+        "static": false,
+        "graded": true,
+        "options": {
+          "choices": [
+            {
+              "correct": false,
+              "content": "Less than halfway through the race"
+            },
+            {
+              "correct": true,
+              "content": "Halfway through the race"
+            },
+            {
+              "content": "More than halfway through the race"
+            }
+          ],
+          "randomize": false,
+          "multipleSelect": false,
+          "countChoices": false,
+          "displayCount": null,
+          "hasNoneOfTheAbove": false,
+          "deselectEnabled": false
+        },
+        "version": {
+          "major": 1,
+          "minor": 0
+        }
+      }
+    }
+  },
+  "answerArea": {
+    "calculator": false,
+    "chi2Table": false,
+    "periodicTable": false,
+    "tTable": false,
+    "zTable": false
+  },
+  "itemDataVersion": {
+    "major": 0,
+    "minor": 1
+  },
+  "hints": []
+}