diff --git a/package.json b/package.json
index 16cf40d..2262f8f 100644
--- a/package.json
+++ b/package.json
@@ -12,9 +12,11 @@
   "files": [
     "demo.html",
     "dist",
-    "lib"
+    "lib",
+    "types"
   ],
   "main": "./lib/index.js",
+  "types": "./types/index.d.ts",
   "scripts": {
     "lint": "eslint .",
     "test": "nyc mocha",
diff --git a/types/index.d.ts b/types/index.d.ts
new file mode 100644
index 0000000..5a4ff61
--- /dev/null
+++ b/types/index.d.ts
@@ -0,0 +1,127 @@
+/**
+ * An item to be layout.
+ */
+type JustifiedLayoutItem = number | { width: number; height: number };
+
+/**
+ * Options for configuring the justified layout.
+ */
+interface JustifiedLayoutOptions {
+    /**
+     * The width that boxes will be contained within irrelevant of padding.
+     * @default 1060
+     */
+    containerWidth?: number | undefined;
+    /**
+     * Provide a single integer to apply padding to all sides or provide an object to apply
+     * individual values to each side.
+     * @default 10
+     */
+    containerPadding?: number | { top: number; right: number; left: number; bottom: number } | undefined;
+    /**
+     * Provide a single integer to apply spacing both horizontally and vertically or provide an
+     * object to apply individual values to each axis.
+     * @default 10
+     */
+    boxSpacing?: number | { horizontal: number; vertical: number } | undefined;
+    /**
+     * It's called a target because row height is the lever we use in order to fit everything in
+     * nicely. The algorithm will get as close to the target row height as it can.
+     * @default 320
+     */
+    targetRowHeight?: number | undefined;
+    /**
+     * How far row heights can stray from targetRowHeight. `0` would force rows to be the
+     * `targetRowHeight` exactly and would likely make it impossible to justify. The value must
+     * be between `0` and `1`.
+     * @default 0.25
+     */
+    targetRowHeightTolerance?: number | undefined;
+    /**
+     * Will stop adding rows at this number regardless of how many items still need to be laid
+     * out.
+     * @default Number.POSITIVE_INFINITY
+     */
+    maxNumRows?: number | undefined;
+    /**
+     * Provide an aspect ratio here to return everything in that aspect ratio. Makes the values
+     * in your input array irrelevant. The length of the array remains relevant.
+     * @default false
+     */
+    forceAspectRatio?: boolean | number | undefined;
+    /**
+     * If you'd like to insert a full width box every n rows you can specify it with this
+     * parameter. The box on that row will ignore the targetRowHeight, make itself as wide as
+     * `containerWidth - containerPadding` and be as tall as its aspect ratio defines. It'll
+     * only happen if that item has an aspect ratio >= 1. Best to have a look at the examples to
+     * see what this does.
+     * @default false
+     */
+    fullWidthBreakoutRowCadence?: boolean | number | undefined;
+    /**
+     * By default we'll return items at the end of a justified layout even if they don't make a
+     * full row. If false they'll be omitted from the output.
+     * @default true
+     */
+    showWidows?: boolean | undefined;
+    /**
+     * If widows are visible, how should they be laid out?
+     * @default "left"
+     */
+    widowLayoutStyle?: 'left' | 'justify' | 'center' | undefined;
+}
+
+/**
+ * Computed positional and sizing properties of a box in the layout.
+ */
+interface LayoutBox {
+    /**
+     * Aspect ratio of the box.
+     */
+    aspectRatio: number;
+    /**
+     * Distance between the top side of the box and the top boundary of the justified layout.
+     */
+    top: number;
+    /**
+     * Width of the box in a justified layout.
+     */
+    width: number;
+    /**
+     * Height of the box in a justified layout.
+     */
+    height: number;
+    /**
+     * Distance between the left side of the box and the left boundary of the justified layout.
+     */
+    left: number;
+    /**
+     * Whether or not the aspect ratio was forced.
+     */
+    forcedAspectRatio?: boolean;
+}
+
+/**
+ * Results from calculating the justified layout.
+ */
+interface JustifiedLayoutResult {
+    /**
+     * Height of the container containing the justified layout.
+     */
+    containerHeight: number;
+    /**
+     * Number of items that are in rows that aren't fully-packed.
+     */
+    widowCount: number;
+    /**
+     * Computed positional and sizing properties of a box in the justified layout.
+     */
+    boxes: LayoutBox[];
+}
+
+declare function justifiedLayout(
+    items: ReadonlyArray<JustifiedLayoutItem>,
+    options?: JustifiedLayoutOptions,
+): JustifiedLayoutResult;
+
+export = justifiedLayout;