What is an IPv6 subnet mask?

IPv6 uses prefix length notation instead of subnet masks, such as /64 or /48. The prefix length specifies how many bits represent the network portion. For example, /64 means the first 64 bits are the network prefix and the remaining 64 bits are for host identification.

How is an IPv6 address compressed?

IPv6 compression rules: (1) Omit leading zeros — leading zeros in each 16-bit group can be removed, e.g. :0001: becomes :1:; (2) Double colon — one contiguous sequence of all-zero groups can be replaced with :: (only once per address). For example, 2001:0db8:0000:0000:0000:0000:1428:57ab becomes 2001:db8::1428:57ab.

Is my data uploaded to any server?

All calculations are performed locally in your browser using pure JavaScript. Your IP address data is never uploaded to any server. You can use this tool offline and in private network environments. No registration or login required.

How is IPv6 subnetting different from IPv4?

IPv6 subnetting is simpler and more flexible. The recommended minimum end-subnet is /64 (supports SLAAC auto-configuration), /48 is typically allocated to enterprise sites, and /32 to ISPs. IPv6 does not require NAT, has a vast 128-bit address space, and subnetting is mainly for route aggregation and management convenience rather than address conservation.

Free IPv6 Subnet Calculator - IPv6 CIDR Subnetting Tool

🔧 Input Parameters

IPv6 Address

Common Prefix Lengths

/32 /36 /40 /44 /48 /52 /56 /60 /64 /96 /112 /120 /127 /128

📊 Calculation Results

Network Address (Compressed)

Network Address (Full)

First Usable Address

Last Usable Address

Total Usable Addresses

Usable /64 Subnets

Prefix Length

Address Type

📖 IPv6 Subnetting Quick Reference

Prefix Length	Usable Addresses	Common Use
/32	2^96 ≈ 7.9×10^28	ISP allocation
/48	2^80 ≈ 1.2×10^24	Enterprise site (recommended)
/56	2^72 ≈ 4.7×10^21	Small site
/64	2^64 ≈ 1.8×10^19	End subnet (SLAAC)
/127	2	Point-to-point link (RFC 6164)
/128	1	Single address / loopback