Calculate DHCP pool range and total leases from a subnet. Exclude reserved IPs and generate a ready-to-paste config.
Enter a subnet to calculate DHCP scope parameters
The DHCP Calculator computes the assignable IP range within any subnet and shows exactly how many leases are available. Enter a subnet in CIDR notation and optionally exclude gateway addresses, static reservations, or any range you want kept out of the pool. The network and broadcast addresses are always excluded automatically.
The config generator produces a ready-to-paste snippet for three common DHCP server platforms. ISC DHCP (used on Linux and many routers), MikroTik RouterOS, and Windows DHCP Server all use different syntax but the same underlying pool start, end, and lease time values computed from your input.
Long enough that clients do not renew all the time, short enough that the addresses of devices that left come back to the pool. Common choices: 8 days (the default of Windows Server DHCP) or 24 hours for offices with the same devices every day, 1 to 4 hours for guest Wi-Fi and busy public networks. A client renews at half of its lease and asks any server at seven eighths (RFC 2131), so a short lease mostly adds renewal traffic, not outages.