Network Range Calculator
Network documentation usually lists a subnet as something like 172.16.8.0/22, but firewall rules, DHCP scopes, and asset inventories often need the actual first and last addresses spelled out. Guessing the range from the prefix is slow and error-prone, especially with less common sizes like /22 or /27. Our free Network Range Calculator takes any starting IP address plus its CIDR prefix and instantly spells out the full range: the network address, the first and last usable addresses, the broadcast address, and the total address count.
How to Use the Network Range Calculator
- Enter any IP address inside the subnet, for example 172.16.10.20.
- Enter the CIDR prefix length from 0 to 32, for example 22.
- Click the Calculate button.
- Review the network address, range start and end, broadcast address, and totals.
- Click Reset to calculate a different subnet.
Worked Example
Imagine your documentation says the branch office uses 172.16.10.20/22 and you need the full range for a firewall rule. Enter the address and prefix, then click Calculate. The tool reports a network address of 172.16.8.0 and a broadcast address of 172.16.11.255. The usable range runs from 172.16.8.1 to 172.16.11.254, with 1,024 total addresses and 1,022 usable hosts. You can paste the exact range 172.16.8.1 – 172.16.11.254 into your firewall policy or DHCP scope with complete confidence.
More Helpful Information
The tool first snaps your starting address down to the true network address by zeroing the host bits, which is why entering 172.16.10.20/22 correctly yields the 172.16.8.0 network rather than anything containing 10.20. This normalization is the step people most often get wrong by hand, because the interesting octet rarely looks like the network boundary. Trusting the calculated network address instead of the address you typed is the key habit.
Range math follows a simple pattern worth memorizing. The number of host bits is 32 minus the prefix, so a /22 leaves 10 host bits and 1,024 addresses. Each time the prefix grows by one, the range halves; each time it shrinks by one, the range doubles. That is why a /23 holds 512 addresses, a /24 holds 256, and a /25 holds 128. Once you internalize the doubling pattern, you can sanity-check any calculator output in seconds.
For firewall and access-list work, always use the full usable range rather than the network-to-broadcast span, since the endpoints cannot be assigned to hosts. When carving DHCP scopes, leave the low addresses for gateways and infrastructure and the high addresses for printers and static devices, then assign the dynamic pool from the middle. If two ranges you calculate overlap, you have found an addressing conflict that would cause intermittent connectivity problems, so renumber one of the subnets before deploying.
Common mistakes include assuming the range starts at the address you typed, forgetting that the broadcast address is not usable, and mixing up similar prefixes like /22 and /23, which differ by a factor of two in size. When in doubt, recalculate rather than editing an old range by hand.
Frequently Asked Questions
1. What is an IP range?
The complete span of addresses in a subnet, usually expressed as the first usable address through the last usable address.
2. How do I find the range from a CIDR?
Calculate the network address, add one for the first usable host, then calculate the broadcast address and subtract one for the last usable host.
3. Why does the range differ from the address I typed?
The address you type can be any host in the subnet. The tool normalizes it down to the true network boundary first.
4. How many addresses are in a /22?
A /22 contains 1,024 total addresses with 1,022 usable for hosts.
5. Can I assign the first address in the range to a device?
Yes. The range start shown here is the first usable host, which is safe to assign. The network address itself is not.
6. What is the broadcast address used for?
It delivers a packet to every host in the subnet at once, used by protocols like ARP and DHCP discovery.
7. Do /31 and /32 subnets have a usable range?
A /31 has two usable addresses and no broadcast, while a /32 is a single host with a range of one address.
8. How do I check whether two ranges overlap?
Calculate both ranges. If the start of one falls inside the other, the subnets overlap and need renumbering.
9. Should firewall rules use the network address or the range?
Use the usable range or CIDR notation. Including the network and broadcast addresses in a rule is harmless but imprecise.
10. What is a DHCP scope?
The portion of the usable range a DHCP server may assign automatically, typically carved from the middle of the subnet.
11. Why do my /22 calculations keep coming out wrong by hand?
Because the boundary falls in the third octet at a multiple of 4, which is easy to misjudge. The calculator removes the guesswork.
12. Can I split a range into smaller subnets?
Yes. Lengthening the prefix divides the range; a /22 splits cleanly into two /23s or four /24s.
13. What does 172.16.0.0/12 mean?
It is the private address block from 172.16.0.0 to 172.31.255.255, containing about one million addresses.
14. How should I document IP ranges?
Record the CIDR, the network and broadcast addresses, the usable range, the gateway, and the DHCP scope for every subnet.
15. Does the range include the gateway?
Yes, the gateway is normally the first usable address inside the range, commonly the .1 address.
CONCLUSION
Accurate ranges are the foundation of reliable firewall rules, DHCP scopes, and network documentation. Bookmark this Network Range Calculator and use it every time you need the exact first and last address of a subnet. Precision here prevents the overlap and addressing mistakes that cause the hardest-to-diagnose outages.