CIDR Calculator
Expand a CIDR block into its full address range, or aggregate a start-to-end IP range into the smallest set of CIDR blocks.
CIDR to IP range
- Network
- 10.20.0.0/22
- Netmask
- 255.255.252.0
- Wildcard
- 0.0.3.255
- First host
- 10.20.0.1
- Last host
- 10.20.3.254
- Broadcast
- 10.20.3.255
- Total addresses
- 1,024
- Usable hosts
- 1,022
IP range to CIDR
10 blocks cover this range.
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CIDR notation, briefly
CIDR (Classless Inter-Domain Routing) writes a network as an address plus a prefix length, like 10.20.0.0/22. The prefix says how many leading bits are the network portion; the rest address hosts. A /24 holds 256 addresses (254 usable), a /22 holds 1024, and each step down doubles the size.
Aggregating a range into CIDR blocks
An arbitrary start-to-end range rarely lines up with a single power-of-two block, so it is expressed as the smallest set of aligned CIDR blocks that exactly covers it. This is what routers and firewalls do internally, and it is handy when a provider hands you a range rather than a clean subnet.
