Printable binary worksheets with answer keys for computing lessons: binary to decimal, secret messages in ASCII, and hexadecimal. Each PDF is 2 pages, sheet plus key. Binary to decimal: place values with a worked example, 10 conversions each way, padding numbers to 8 bits, counting from 8 to 15 in 4 bits, and two reasoning questions. Secret messages in binary: an A to Z table of 8-bit ASCII codes, three messages to decode, four to encode, and a name-swap activity for pairs. Hexadecimal: hex digits as 4 bits, hex to decimal and back, hex to binary, and splitting web color codes into red, green and blue. Print page 1 for students and keep page 2 as the answer key. The sheets print on US Letter; on A4, choose Fit to page. Students can check their answers with the free converters at binarytranslator.ai, where the worksheets page always has the latest version.