Subnet Calculator – Free Online Tool
Calculate IPv4 CIDR ranges, subnet masks, wildcard masks, host capacity, and child subnets with beginner-friendly diagnostics.
Free IPv4 Subnet Calculator and CIDR Calculator
ToolsMint Subnet Calculator turns an IPv4 address or CIDR block into the numbers network admins, developers, cloud engineers, and students need: network address, broadcast address, first usable host, last usable host, total addresses, usable hosts, subnet mask, wildcard mask, and binary notation.
Subnet Mask, Wildcard Mask, and Host Range in One View
Instead of making you calculate octets by hand, the tool converts CIDR notation such as /24, /26, /29, /31, and /32 into a clear range summary. It also explains special cases like point-to-point /31 links and single-host /32 routes.
Subnet Splitter for VPCs, LANs, and Firewall Rules
Use the subnet splitter to divide a parent block into smaller child networks. This is useful when planning cloud VPC subnets, VLANs, lab networks, firewall allowlists, router ACLs, load balancer ranges, VPN pools, and segmented office networks.
Private IP and Reserved Range Diagnostics
The built-in assistant labels private RFC 1918 ranges, public routable addresses, loopback, link-local, carrier-grade NAT, documentation blocks, multicast, and reserved ranges. It also warns when an input host is automatically adjusted to its network address.
Private Browser-Based Network Planning
Subnet calculations, subnet splitting, diagnostics, copy actions, JSON reports, and CSV exports run locally in your browser. No account is required, and your IP planning notes are not uploaded to ToolsMint.
Frequently Asked Questions
Everything you need to know about the Subnet Calculator.
Is this subnet calculator free?
Yes. It is free to use with no signup, no account, and no usage limit.
What does a CIDR prefix mean?
The CIDR prefix is the number after the slash. A /24 fixes the first 24 bits for the network and leaves 8 bits for host addresses.
Can I calculate the subnet mask from CIDR?
Yes. Enter a CIDR block such as 10.0.0.0/16 or 192.168.1.0/24 and the tool shows the subnet mask and wildcard mask.
Does the tool support /31 and /32 networks?
Yes. /31 is handled as a two-address point-to-point link, and /32 is handled as a single-host route.
Can I split a subnet into smaller subnets?
Yes. Use the split slider to preview child CIDR blocks and export the first 256 rows as CSV for planning.
Are my IP addresses uploaded?
No. IPv4 parsing, subnet math, diagnostics, copying, JSON export, and CSV export run locally in your browser.