IP Range Calculator
Convert a start and end IP address into the CIDR blocks that cover it, and count the addresses in a range.
Your details
This calculator runs entirely on your device. Nothing you enter is uploaded, stored, or sold. How this works
Addresses in range
191
192.168.1.10 to 192.168.1.200 — covered by 8 CIDR blocks
Includes your inputs, the full breakdown, and every row of the table.
Start address
192.168.1.10
End address
192.168.1.200
CIDR blocks required
8
Equivalent /24s
0.75
- Start (integer)
- 3,232,235,786
- End (integer)
- 3,232,235,976
- Total addresses
- 191
- Blocks needed
- 8
| CIDR | First address | Last address | Size |
|---|---|---|---|
| 192.168.1.10/31 | 192.168.1.10 | 192.168.1.11 | 2 |
| 192.168.1.12/30 | 192.168.1.12 | 192.168.1.15 | 4 |
| 192.168.1.16/28 | 192.168.1.16 | 192.168.1.31 | 16 |
| 192.168.1.32/27 | 192.168.1.32 | 192.168.1.63 | 32 |
| 192.168.1.64/26 | 192.168.1.64 | 192.168.1.127 | 64 |
| 192.168.1.128/26 | 192.168.1.128 | 192.168.1.191 | 64 |
| 192.168.1.192/29 | 192.168.1.192 | 192.168.1.199 | 8 |
| 192.168.1.200/32 | 192.168.1.200 | 192.168.1.200 | 1 |
What this means
- Arbitrary IP ranges rarely align to a single CIDR block. The list above is the minimal set of blocks that exactly covers your range with no overflow.
- Firewall rules, route tables, and security groups all expect CIDR notation, so this conversion is the usual bridge between a human-readable range and a device configuration.
How the ip range calculation works
IP addresses are 32-bit integers, so any range between two addresses is just the difference between two numbers plus one. Converting that range into CIDR blocks is harder, because each block must start on a boundary that matches its size.
The algorithm works greedily: at each position, find the largest block that both aligns to the current address and does not overshoot the end of the range, emit it, then advance. The result is the minimal covering set.
Frequently asked questions
Why does my range need multiple CIDR blocks?
A CIDR block must start at an address divisible by its size. A range like .10 to .200 does not align to any single power-of-two boundary, so it decomposes into several blocks.
How many IPs are in a range?
End minus start, plus one. The range 10.0.0.1 to 10.0.0.10 contains ten addresses, not nine.
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Disclaimer. This calculator is provided for general information and educational purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Results are estimates based on the inputs you provide and the assumptions described above. Confirm any figure with a qualified professional before acting on it.