Binary Multiplication Calculator

How it is calculated

Type two binary numbers in bin1 and bin2, each made only of the digits 0 and 1 and at most 20 digits long. The tool converts both to ordinary integers, multiplies them, and writes the product back in base 2: product = bin1 × bin2. It shows two results, the binary product and its decimal value, which is handy for checking by hand. Leading zeros are accepted and dropped. Anything else is rejected without a message and gives no result: digits 2 to 9, a minus sign, a point, spaces inside the number, or more than 20 digits. Only the final product is shown, not the partial rows of the long multiplication.

Common mistakes

• Typing decimal numbers such as 11 and 6. Digits above 1 are rejected, so 102 gives no result; enter 1011 and 110 for those values.
• Entering a negative binary number with a minus sign or two's complement. Only unsigned 0 and 1 strings are accepted.
• Forgetting the binary carry when checking by hand: 1 + 1 = 10, not 2. Use the decimal line as a cross-check.
• Entering numbers longer than 20 digits. The input is limited to 20 binary digits each, and a longer string returns nothing rather than a trimmed answer.