📚 What Is an IP Range?
An IP range is a consecutive sequence of IP addresses between a start address and an end address. In IPv4, every address is a 32-bit integer — meaning ranges can be manipulated mathematically. The most common way to express a range is CIDR notation (e.g. 192.168.1.0/24), but ranges can also be written as explicit start–end pairs (e.g. 192.168.1.0 – 192.168.1.255).
IP ranges are foundational to networking: routers match packets to routes using ranges, firewalls permit or deny traffic by ranges, and geolocation databases store (start, end, location) tuples to map billions of IPs. Understanding IP ranges helps you design networks, configure security policies, and troubleshoot connectivity.
🔢 How to Calculate an IP Range from CIDR
CIDR notation encodes both the network address and the prefix length. To calculate the range:
- Convert the IP to a 32-bit binary number.
- The first prefix bits are the network bits (fixed). The remaining 32 − prefix bits are host bits.
- Set all host bits to 0 → Network Address (range start).
- Set all host bits to 1 → Broadcast Address (range end).
- Total addresses = 2(32−prefix). Usable hosts = Total − 2.
Example: 192.168.1.0/24 → 8 host bits → 28 = 256 total → 254 usable hosts (192.168.1.1 – 192.168.1.254).
🛡️ Use Cases for IP Range Calculations
🔒
Firewall & ACL Rules
Define permit/deny rules using CIDR ranges to block entire geographic regions or malicious ASN prefixes. One CIDR rule replaces thousands of individual IP entries.
📊
Network Segmentation
Design VLANs and subnets by allocating IP ranges per department or workload. A /26 (62 hosts) per floor — allocate them from a parent /22.
🔍
Penetration Testing
Define engagement scope as CIDR blocks. nmap, masscan, and Shodan accept CIDR input directly. Confirm exact host counts before scanning.
🌐
Cloud Security Groups
AWS/GCP/Azure security groups use CIDR. Restrict DB access to 10.0.1.0/24 (app subnet) instead of 0.0.0.0/0. Our calculator confirms the tightest CIDR for any range.
📌
IP Geolocation Databases
MaxMind GeoLite2 stores IP ranges as start–end integer pairs. Converting CIDR to integer pairs (this calculator's output) is the exact format used internally.
📡
DHCP Pool Planning
Calculate usable host range first, then reserve static IPs at the low end and set the DHCP pool at the high end to prevent conflicts.
🔗 More Ways to Work With IP Ranges
For full subnet splitting (VLSM), use our Subnet Calculator. For detailed CIDR mathematics including wildcard masks, try the CIDR Calculator. For geolocation and ASN data on any IP, use IP Lookup. Check ranges against blocklists with our Blacklist Checker. For understanding IP addresses deeper, read What Is an IP Address? and Public vs Private IP.
What is an IP range? +
An IP range is a consecutive sequence of IP addresses between a start address and an end address. Ranges can be expressed as CIDR notation (e.g. 192.168.1.0/24) or as explicit start–end pairs (e.g. 192.168.1.1 – 192.168.1.254).
How do I calculate the number of IPs in a CIDR block? +
The formula is 2^(32-prefix). For /24: 256 total (254 usable). For /16: 65,536. For /28: 16 (14 usable). This calculator does the math instantly.
What is the difference between network address and usable hosts? +
The first address (network) and last address (broadcast) are reserved and cannot be assigned to devices. A /24 with 256 total IPs yields 254 usable host addresses.
Can I calculate the range between two IPs without CIDR? +
Yes — use the Start–End tab. The calculator converts both to 32-bit integers, finds the count, and shows covering CIDR blocks.
What is IP range used for in firewalls? +
Firewall ACLs use CIDR ranges to permit or deny traffic from groups of addresses. One CIDR rule replaces thousands of individual IP entries.
How do I check if an IP is within a range? +
Convert the target IP and both range endpoints to 32-bit integers. If start_int ≤ ip_int ≤ end_int, the IP is in range. Use the IP in Range Check tab above.
What is the largest IPv4 range? +
0.0.0.0/0 is the default route covering all 4,294,967,296 IPv4 addresses. /32 is the smallest — a single host.
What are private IP ranges? +
RFC 1918: 10.0.0.0/8 (16.7M IPs), 172.16.0.0/12 (1M IPs), 192.168.0.0/16 (65K IPs). Not routed on the public internet.
How are IP ranges used in geolocation databases? +
Geolocation DBs store (start_int, end_int, country, city, ISP) rows. Binary search finds your IP's row — that's why lookup is instant even for billions of IPs.
What is a reserved IP range? +
127.0.0.0/8 (loopback), 169.254.0.0/16 (link-local/APIPA), 224.0.0.0/4 (multicast), 240.0.0.0/4 (experimental/future use). This calculator flags these automatically.
Can one IP belong to multiple ranges? +
Yes. 192.168.1.5 belongs to /24, /16, and /8 ranges simultaneously. The longest prefix match (most specific) wins in routing decisions.
How do I convert an IP range to CIDR? +
If the range start has all host bits zero and count is a power of 2, it maps to one CIDR. Otherwise multiple CIDRs are needed. Our Start–End mode shows the minimum CIDR set.
How is IP range used in cloud security groups? +
AWS, GCP, Azure security groups use CIDR notation. Restrict database access to 10.0.1.0/24 (app subnet) instead of 0.0.0.0/0 to limit exposure.
How many total IPv4 addresses exist? +
2^32 = 4,294,967,296 total. Roughly 3.7 billion are publicly routable after subtracting reserved and private ranges.
How is IP range used in penetration testing? +
Pen testers define scope as CIDR blocks. nmap/masscan/Shodan accept CIDR directly. Always confirm IP counts before scanning to stay in scope.
Is the IP Range Calculator free? +
Yes — completely free, browser-only, no account. No IP data is sent to our servers.