Subnet Calculator Online
Enter an IPv4 CIDR block to see network address, broadcast, subnet mask, wildcard mask, total and usable hosts, usable range, and binary representations. Convert a dotted mask to a CIDR prefix and use the quick-reference table for common sizes.
- Private & secure
- Fast in-browser
- No signup
How to use Subnet Calculator Online
- Open the tool. Go to Subnet Calculator on Utilvia. It runs instantly in your browser.
- Enter your values. Fill in the fields. Results update as you type — no signup required.
- Review the output. Check totals, breakdowns, or formatted text before you copy or save.
- Copy or export. Copy the result or download a file. Your inputs stay on this device.
Key features & privacy
Subnet Calculator Online is built for in-browser use on Utilvia. Work stays on this device whenever the tool runs locally — there is no account wall and no file inbox on our servers.
- Runs in modern browsers with JavaScript and HTML5.
- No signup required to get a result.
- Zero-upload policy on local-first tools — close the tab and the working copy is gone.
- Shareable, indexable URL so you can return to the same utility later.
Frequently asked questions
What does /24 mean in an IP address like 192.168.1.0/24?
The /24 prefix means the first 24 bits are the network. That is a 255.255.255.0 mask with 256 addresses and 254 usable hosts.
Why are 2 addresses subtracted from the total to get usable hosts?
The first address is typically the network and the last is broadcast. /31 and /32 do not reserve those two addresses the same way.
What's the difference between a subnet mask and a CIDR prefix?
They describe the same split. /24 is the count of network bits; 255.255.255.0 is those bits as four octets.
Is my data private when using Subnet Calculator?
Yes. The calculator runs entirely in your browser. Your inputs are never uploaded to Utilvia servers.
Do I need to create an account?
No. It is free to use with no signup or login required.