What is 9 in binary?
9₁₀ converted to binary is 1001₂. 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.
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How to convert 9 to binary, step by step
Keep dividing 9 by 2 and writing down each remainder. The remainders, read in reverse, are the answer.
| Number | ÷ 2 | Quotient | Remainder |
|---|---|---|---|
| 9 | 2 | 4 | 1 |
| 4 | 2 | 2 | 0 |
| 2 | 2 | 1 | 0 |
| 1 | 2 | 0 | 1 |
Reading the remainder column from the bottom up gives 1001, so 9₁₀ = 1001₂. Check it back: 8 + 1 = 9 — the 1 bits add up to 9.
In short: 9 ÷ 2 = 4 r 1 → 4 ÷ 2 = 2 r 0 → 2 ÷ 2 = 1 r 0 → 1 ÷ 2 = 0 r 1 → read bottom-up: 1001₂
Frequently asked questions
How do you write 9 in binary?
Divide 9 by 2 over and over, noting each remainder: 9 ÷ 2 = 4 r1, 4 ÷ 2 = 2 r0, 2 ÷ 2 = 1 r0, 1 ÷ 2 = 0 r1. Reading the remainders from last to first gives 1001, so 9₁₀ = 1001₂.
How long is 9 in binary?
9 in binary is 1001, which is 4 bits long. It ends in 1 because 9 is odd — the last bit of any binary number tells you odd (1) or even (0).
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