⬡ Subnet Calculator
IPv4 subnetting — enter any address and prefix to see full network details and binary breakdown.
Binary Breakdown
Frequently Asked Questions
Do you get a calculator on the CompTIA Network+ exam?
No. The CompTIA Network+ (N10-009) exam does not provide an on-screen calculator, and you can't bring your own. Subnetting questions must be answered by hand using the scratch note board the test center provides (or the digital whiteboard on online-proctored exams). Use this calculator to practice and check your work while studying, then learn to subnet mentally with the magic-number method for exam day.
How do you subnet without a calculator on the Network+ exam?
Use the magic-number method: subtract the interesting octet of the subnet mask from 256 to get the block size, then list the subnet boundaries from there. It lets you find the network address, broadcast address, and host range of any IPv4 prefix in under 30 seconds, entirely in decimal, with no calculator.
Is this subnet calculator free?
Yes. The IPv4 subnet calculator on it-learn.io is completely free, with no sign-up required, and is built specifically for CompTIA Network+ N10-009 exam preparation.