Hex Addition Calculator

How it is calculated

Each hex number is read as base 16, added, and the sum is written back in base 16. In symbols, sum = a + b, where a and b are the values of the two inputs (digits 0 to 9 and letters A to F, upper or lower case, each digit worth 16 times the digit to its right). The tool adds digit by digit with carries at 16, so it is exact and does not depend on floating-point numbers. It shows the sum in hex (in capitals), the sum in decimal and the decimal value of each input. Each operand may have up to 64 hex digits (256 bits); leading zeros are ignored, and a longer operand gives no result. Only plain hex digits are accepted: a 0x prefix, a #, a minus sign, spaces inside the number or an empty box give no result.

Common mistakes

• Typing a 0x prefix, as in 0x3E8, or a # as in a colour code. Only the digits are accepted, and the prefix makes the tool return nothing.
• Adding hex digits as if they were decimal, for example thinking that 9 + 1 = 10 in hex. In hex, 9 + 1 = A, and the carry happens at 16, so F + 1 = 10.
• Entering a decimal number such as 1000 and reading it as hex. The tool reads 1000 as hex, which is 4,096 in decimal.
• Expecting negative numbers. A minus sign is not accepted, so for a subtraction use a different tool.
• Pasting a value longer than 64 hex digits, such as a 512-bit key. Operands over 64 digits are rejected rather than truncated.