IPv4 Subnet & Range Mask Calculator
Use this ip range mask calculator to convert between CIDR and subnet masks, find network/broadcast addresses, and summarize an IP range into CIDR blocks.
1) IP + Mask / CIDR
2) IP Range to CIDR Blocks
What an IP Range Mask Calculator Does
An ip range mask calculator helps you quickly answer common subnetting questions without doing manual binary math each time. You provide an IPv4 address with a subnet mask (or CIDR prefix), and the calculator returns practical details such as network ID, broadcast address, first and last usable host, and host counts.
For planning and troubleshooting, this saves time and reduces mistakes. Instead of manually translating /27 into 255.255.255.224, you can calculate immediately and validate whether an address belongs to the expected subnet.
Why Network Engineers Use This Constantly
- Subnet design: carve large ranges into smaller VLAN networks.
- Firewall rules: verify exact address boundaries before allowing/denying traffic.
- Cloud setup: avoid overlapping VPC/VNet CIDR blocks.
- Troubleshooting: check if two devices are on the same subnet.
- Documentation: convert human-friendly ranges into correct CIDR notation.
Quick CIDR Reference
Common Prefixes
/24=255.255.255.0(256 addresses, 254 typical usable)/25=255.255.255.128(128 addresses)/26=255.255.255.192(64 addresses)/27=255.255.255.224(32 addresses)/28=255.255.255.240(16 addresses)/30=255.255.255.252(4 addresses, often point-to-point)
How to Use This Calculator
Mode 1: IP + Mask
Enter a single IPv4 address and either a CIDR prefix (/24) or dotted decimal mask (255.255.255.0). The tool calculates your full subnet profile instantly.
Mode 2: Start/End Range
Enter start and end IP addresses. The calculator returns:
- the smallest single subnet that covers the full range, and
- the exact list of CIDR blocks required to represent the range precisely.
This is useful when you receive arbitrary ranges from policy, vendors, or legacy systems.
Common Mistakes to Avoid
- Using non-contiguous subnet masks (invalid in normal IPv4 subnetting).
- Assuming all ranges can be represented by one CIDR block exactly.
- Forgetting that
/31and/32are special cases. - Mixing private and public address assumptions during ACL design.
Final Thoughts
A dependable ip range mask calculator is one of the highest-leverage tools for network design and operations. Whether you are configuring routers, documenting IP plans, or auditing firewall entries, accurate subnet math prevents outages and saves hours of rework.