The subnet calculator takes an IPv4 address and CIDR prefix length and computes the network address, broadcast address, first and last host, and the number of usable hosts in the subnet.
Use Subnet Calculator when you need a quick other estimate, want to compare different inputs, or need a clear result without setting up a spreadsheet.
Enter the values requested in the calculator, run the calculation, and review the result. If the tool offers multiple modes, choose the mode that matches the question you are trying to answer before comparing outputs.
Read the output together with the inputs you entered. Change one input at a time to see which assumptions have the biggest effect, especially for finance, health, tax, or planning calculations.
This calculator is a simplified planning tool. It cannot account for every personal, legal, medical, tax, or financial detail, so use the result as a starting point and verify important decisions with qualified guidance.