Each subnet bit halves the hosts

Every bit moved from host to network halves the addresses — a /24 has 254 usable.

Why it works

2^(host bits) minus network and broadcast. /25 → 126, /26 → 62, /30 → 2 (the classic point-to-point link).

Do it exactly

Estimate with the rule, then check it against the calculator that models it properly.

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More in Computers

• 2¹⁰ ≈ 10³Every 10 bits multiplies by ~1,000 — kibi and kilo differ by just 2.4%.
• RAID is not a backupRAID protects against disk failure — deletion, ransomware and fat fingers replicate instantly.
• 3-2-1 backupsKeep 3 copies of anything that matters, on 2 different media, with 1 off-site.
• The ×100 latency ladderRAM ~100 ns, SSD ~100 µs, spinning disk ~10 ms — each rung roughly 100× slower.

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