Subnet Calculator · free online developer tool
CIDR and IP range math with host count and mask. No install, opens instantly, works offline — data stays in your browser.
How to use Subnet Calculator
- Open this page (or search “Subnet Calculator” on www.258tool.com).
- Enter your input in the tool panel — results update instantly.
- Copy, download or save as needed; your data is stored locally on this device.
FAQ
Is Subnet Calculator free?
Completely free. No sign-up, no account — open and use.
Is my data uploaded to a server?
No. All processing runs locally in your browser; data stays on your device.
Does Subnet Calculator work offline?
Yes. After the first visit, add 258tool to your home screen and everything works offline.
ReferenceIETF RFC 791(IP)与 RFC 4632(CIDR)地址划分规范