What is 42 in binary?
42₁₀ converted to binary is 101010₂. The complete working for this exact number is below — or type a different number into the decimal to binary converter and watch it happen live.
Try it yourself — instant converter
See the steps for your number
How to convert 42 to binary, step by step
Keep dividing 42 by 2 and writing down each remainder. The remainders, read in reverse, are the answer.
| Number | ÷ 2 | Quotient | Remainder |
|---|---|---|---|
| 42 | 2 | 21 | 0 |
| 21 | 2 | 10 | 1 |
| 10 | 2 | 5 | 0 |
| 5 | 2 | 2 | 1 |
| 2 | 2 | 1 | 0 |
| 1 | 2 | 0 | 1 |
Reading the remainder column from the bottom up gives 101010, so 42₁₀ = 101010₂. Check it back: 32 + 8 + 2 = 42 — the 1 bits add up to 42.
In short: 42 ÷ 2 = 21 r 0 → 21 ÷ 2 = 10 r 1 → 10 ÷ 2 = 5 r 0 → 5 ÷ 2 = 2 r 1 → 2 ÷ 2 = 1 r 0 → 1 ÷ 2 = 0 r 1 → read bottom-up: 101010₂
Frequently asked questions
How do you write 42 in binary?
Divide 42 by 2 over and over, noting each remainder: 42 ÷ 2 = 21 r0, 21 ÷ 2 = 10 r1, 10 ÷ 2 = 5 r0, 5 ÷ 2 = 2 r1, 2 ÷ 2 = 1 r0, 1 ÷ 2 = 0 r1. Reading the remainders from last to first gives 101010, so 42₁₀ = 101010₂.
How long is 42 in binary?
42 in binary is 101010, which is 6 bits long. It ends in 0 because 42 is even — the last bit of any binary number tells you odd (1) or even (0).
Keep converting
← 41 in binary · 43 in binary →
Popular values
10 in binary · 25 in binary · 50 in binary · 100 in binary · 255 in binary