I'm assuming you're using a 255.255.255.0 mask. Changing that to 255.255.0.0 would be more than enough room to grow.

Basic IP addressing & Subnetting I built a basic network lab using a FortiGate 60D as my main firewall/router. Set up WAN & LAN interfaces Configured IP addressing & default gateways Enabled GUI ...

We found several utilities to help calculate IP subnets, subnet ranges, and CIDR addressing. IP Subnet Calculator (free) is a good, basic subnet calculator that shows available subnets based on IP ...