diff --git a/maths/binary_to_decimal.ts b/maths/binary_to_decimal.ts
new file mode 100644
index 00000000..a68108b6
--- /dev/null
+++ b/maths/binary_to_decimal.ts
@@ -0,0 +1,18 @@
+/**
+ * @function binaryToDecimal
+ * @description Convert binary string to decimal.
+ * @param {string} str - The binary input.
+ * @return {number} - Decimal value of str.
+ * @example binaryToDecimal('1100') = 12
+ * @example binaryToDecimal('1110') = 14
+ */
+
+export const binaryToDecimal = (str: string): number => {
+  let number = 0
+
+  for (let i = 0; i < str.length; i++) {
+    number = number * 2 + Number(str[i])
+  }
+
+  return number
+}
diff --git a/maths/test/binary_to_decimal.test.ts b/maths/test/binary_to_decimal.test.ts
new file mode 100644
index 00000000..f5fff43e
--- /dev/null
+++ b/maths/test/binary_to_decimal.test.ts
@@ -0,0 +1,27 @@
+import { binaryToDecimal } from '../binary_to_decimal'
+
+describe('binaryToDecimal', () => {
+  it('should return the correct value', () => {
+    expect(binaryToDecimal('100')).toBe(4)
+  })
+
+  it('should return the correct value', () => {
+    expect(binaryToDecimal('1100')).toBe(12)
+  })
+
+  it('should return the correct value of the sum from two numbers', () => {
+    expect(binaryToDecimal('1110')).toBe(12 + 2)
+  })
+
+  it('should return the correct value of the subtract from two numbers', () => {
+    expect(binaryToDecimal('10111101')).toBe(245 - 56)
+  })
+
+  it('should return the correct value', () => {
+    expect(binaryToDecimal('11111110')).toBe(254)
+  })
+
+  it('should return the correct value', () => {
+    expect(binaryToDecimal('1111011111111011')).toBe(63483)
+  })
+})