Calculate IPv4 Subnets Online
Find CIDR ranges, subnet masks, host counts and broadcast addresses
| Network Address | 192.168.1.0 | |
| Broadcast Address | 192.168.1.255 | |
| First Usable IP | 192.168.1.1 | |
| Last Usable IP | 192.168.1.254 | |
| Total Usable Hosts | 254 | |
| Subnet Mask | 255.255.255.0 | |
| Wildcard Mask | 0.0.0.255 | |
| CIDR Notation | 192.168.1.0/24 | |
| IP Class | C |
| CIDR | Subnet Mask | Usable Hosts | Common Use |
|---|---|---|---|
/32 | 255.255.255.255 | 1 | Host route |
/31 | 255.255.255.254 | 2 | Point-to-point link |
/30 | 255.255.255.252 | 2 | Small P2P |
/29 | 255.255.255.248 | 6 | Small subnet |
/28 | 255.255.255.240 | 14 | — |
/27 | 255.255.255.224 | 30 | — |
/26 | 255.255.255.192 | 62 | — |
/25 | 255.255.255.128 | 126 | — |
/24 | 255.255.255.0 | 254 | Class C / typical LAN |
/23 | 255.255.254.0 | 510 | — |
/22 | 255.255.252.0 | 1,022 | — |
/21 | 255.255.248.0 | 2,046 | — |
/20 | 255.255.240.0 | 4,094 | — |
/16 | 255.255.0.0 | 65,534 | Class B |
/8 | 255.0.0.0 | 16,777,214 | Class A |
/0 | 0.0.0.0 | 4,294,967,294 | All IPs |
Use this IP Subnet Calculator to calculate IPv4 subnet details from an IP address and CIDR prefix. It helps network engineers, DevOps teams, cloud architects, system administrators, students and developers understand network address, broadcast address, subnet mask, wildcard mask, usable host range and total host capacity. Subnetting mistakes can cause routing issues, overlapping networks, wasted address space or unreachable services. This tool is useful when planning VPCs, private networks, server ranges, firewall rules, lab exercises, access lists or troubleshooting whether two IP addresses belong to the same subnet.
How to Calculate IP Subnet Information
Enter an IP address and drag the CIDR slider — all subnet values calculate instantly.
Enter your IPv4 address
Type any valid IPv4 address into the input field (four octets separated by dots, each between 0 and 255). The field validates the address in real time and shows an error for invalid inputs. A default address of 192.168.1.100 is pre-filled as a starting point.
Set the CIDR prefix length
Drag the slider to select a prefix length from /0 to /32. Common values are /24 (a standard Class C subnet with 254 usable hosts), /16 (a Class B subnet), /8 (a Class A subnet), and /32 (a single host route). You can also click any row in the CIDR reference table at the bottom to jump directly to that prefix length.
Read the calculated values
The results table shows nine values simultaneously: Network Address (the first address in the subnet), Broadcast Address (the last address), First Usable IP (network + 1), Last Usable IP (broadcast - 1), Total Usable Hosts (2 to the power of (32 minus prefix) minus 2), Subnet Mask (dotted decimal), Wildcard Mask (inverse of subnet mask), CIDR Notation (network address with prefix), and IP Class (A, B, C, D for multicast, or E for reserved).
Features
Calculates IPv4 network address from IP and CIDR input
Finds broadcast address for the selected subnet range
Shows first and last usable host addresses clearly
Computes total usable host count for the CIDR prefix
Converts CIDR prefix into dotted-decimal subnet mask
Generates wildcard mask values for routing and ACL workflows
Helps detect whether a subnet is too small or too large
Supports network planning for servers, labs, firewalls and cloud VPCs
Clarifies /24, /28, /30 and other common subnet sizes
Reduces manual binary math errors during subnetting
What This Tool Helps You Do
Calculate IPv4 subnet details without doing binary math by hand. Enter an IP address and CIDR prefix to see the network address, broadcast address, usable range, subnet mask, wildcard mask and host count.
This is useful when planning networks, checking firewall ranges, creating lab environments or confirming whether an address belongs inside a specific subnet.
Why Subnet Planning Matters
A subnet is not just a range of IPs. It affects routing, firewall rules, service reachability and how much address space you have left for future growth. A subnet that is too small can block expansion. A subnet that overlaps another network can break routing or peering.
The unique detail with subnetting is that the first and last addresses often have special meaning: the network address identifies the range, and the broadcast address is usually not assigned to a host.
Practical Ways to Use This Tool
- Calculate the usable host range for a CIDR block
- Convert CIDR prefixes into subnet masks
- Check network and broadcast addresses before configuration
- Plan private network ranges for servers and services
- Verify firewall, routing or access-control ranges
- Use a Number Base Converter when learning the binary logic behind subnet masks
- Review server response behavior with an HTTP Header Analyzer after network changes
- Pair automation schedules with a Cron Expression Builder for network maintenance tasks
What to Check Before Using a Subnet
Check whether the range overlaps with existing networks, VPNs, office networks, cloud VPCs or container networks. Also check reserved addresses. Some environments reserve more than the traditional network and broadcast addresses, so the usable count may be lower than the textbook value.
For production networks, leave room for gateways, load balancers, NAT, monitoring, failover and future services.
Expert Tips
Use smaller subnets for tightly scoped service tiers and larger subnets where growth is expected. Keep naming and documentation clear so future teams know what each range is used for. Avoid choosing ranges only because they are familiar; check overlap before connecting systems.
For troubleshooting, compare the IP, mask and route together. A correct subnet calculation does not guarantee that routing, firewall rules or DNS are correct.
Common Mistakes to Avoid
- Planning a subnet with no room for growth
- Forgetting platform-reserved IP addresses in hosted environments
- Overlapping private ranges across connected networks
- Treating the broadcast address as a normal host address
- Confusing CIDR prefix length with total host count
- Using a /32 when a host route was not intended
- Ignoring firewall rules after calculating the correct range
- Assuming two IPs can communicate just because they are in nearby ranges
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Frequently Asked Questions
What does an IP subnet calculator do?
An IP subnet calculator takes an IPv4 address and CIDR prefix and calculates the network range. It shows values such as subnet mask, network address, broadcast address, usable host range and host count.
How do I calculate a subnet from CIDR?
Enter the IPv4 address and CIDR prefix, such as 192.168.1.10/24. The calculator then uses the prefix length to determine which bits belong to the network and which bits are available for hosts.
Can this help choose the right subnet size?
Yes. Compare the usable host count with the number of devices, servers or services you need. Leave space for growth and any platform-reserved addresses when planning production networks.
Does a /24 subnet always have 254 usable hosts?
In traditional IPv4 subnetting, a /24 has 256 total addresses and usually 254 usable hosts after excluding the network and broadcast addresses. Some cloud platforms may reserve additional addresses.
Is the broadcast address usable?
Normally no. The broadcast address is reserved for sending traffic to all hosts in the subnet. It is not assigned to a regular host in typical IPv4 networks.
Why does /30 only have two usable hosts?
A /30 subnet has four total addresses. One is the network address and one is the broadcast address, leaving two usable addresses, often used for point-to-point links.
When should I use a smaller subnet?
Use a smaller subnet when you need tight address allocation for a limited number of hosts. Avoid making it so small that future services, load balancers, gateways or reserved addresses do not fit.
What is a wildcard mask used for?
A wildcard mask is often used in routing and access-control configurations to describe which address bits should be matched. It is the inverse of a subnet mask.
Can overlapping subnets cause problems?
Yes. Overlapping subnets can create routing ambiguity, failed peering, broken VPN routes or traffic going to the wrong network. Always check ranges before connecting networks.
What should I check before using a subnet in production?
Check usable host count, reserved platform addresses, overlap with existing networks, routing rules, firewall policies and future growth. For cloud setups, also verify provider-specific subnet restrictions.
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