Subnet Calc is a free online IPv4 and IPv6 subnet calculator that also provides IP address management capabilities, primarily for network engineers. Its core purpose is to plan before allocating address space, and to split and manage IPv4 and IPv6 networks.
Main capabilities: Users enter an IPv4 or IPv6 address with a CIDR prefix (for example, 192.168.1.0/24) for calculations; the prefix length determines the address block size, and the larger the prefix, the smaller the subnet. A parent prefix can be split into subnets for different environments, sites, or customers, and the space occupied by each subnet can be viewed. It can also be used to design cloud networks, plan VNet and VPC address schemes, name each subnet, and export results for documentation or deployment.
How to use: The free calculator requires no account; open the page and enter an address to use it. Designs in the free version are saved in browser local storage, limited to the current device, and may be lost after clearing browser data. Paid plans provide cloud projects that can save designs to an account, and include features such as version history, cross-device access, project hierarchy (parent-child relationships, corresponding to network structure), export templates, and team collaboration; team plans provide each member with the same projects and history, giving address planning a single source of truth.
Applicable scenarios: Suitable for network teams to plan before allocating address space, splitting subnets by environment, site, or customer; suitable for VNet and VPC address planning for cloud networks; suitable for teams that need to continue previous designs from any device, view design evolution, or have multiple people share the same address scheme.
Limitations and notes: Cloud projects require a paid plan; merely registering an account does not include cloud projects, and the free tier only covers the local calculator using browser local storage; team collaboration is only available in team plans, and the Individual plan is for a single user. The individual lifetime version is a one-time payment, limited to one user, and is only available while founding member slots remain; the pricing page shows the current price and real-time availability, and once the slots are used up, only annual payment plans are offered. Team plans each have their own member and project limits, subject to the pricing page. The materials do not provide details such as specific prices, amounts, a detailed feature comparison between free and paid versions, or export formats for IPv4/IPv6 calculation results.
