IPv4 Subnet Calculator Online — Calculate CIDR Ranges
Calculate IPv4 network, netmask, broadcast, host range and address counts from CIDR notation locally.
About this tool
This subnet calculator converts an IPv4 address and /0–/32 prefix into unsigned network values and reports network, mask, broadcast, first and last host plus totals.
How to use
- Enter IPv4 CIDR such as 192.168.1.10/24.
- Run the calculation.
- Review the network and usable host range.
Features
- Supports prefixes /0 through /32.
- Calculates network, broadcast and netmask.
- Handles /31 and /32 host counts.
Common use cases
- Plan a private subnet.
- Check whether addresses share a network.
- Verify firewall and routing ranges.
Common issues and tips
- Input must include a valid dotted IPv4 address and prefix.
- Traditional usable-host rules differ for /31 point-to-point networks.
Privacy
Subnet calculation runs locally.
Frequently asked questions
What is CIDR?
It combines an IP address with a prefix length describing network bits.
Are /31 networks supported?
Yes, they report two usable addresses for point-to-point use.
Does it contact the address?
No. It performs arithmetic only.