How Many IPv4 Addresses Are There? Total, Public, and Available

What does 4,294,967,296 count?

The number is the complete set of bit patterns an IPv4 address can hold, from 0.0.0.0 through 255.255.255.255. It is a protocol total before private-use, loopback, multicast, documentation, shared, and other special-purpose ranges are considered. It also says nothing about whether an address is registered to an organization, announced in BGP, accepted by another network, or currently offered for transfer or lease.

IPv4 totals that answer different questions

Count or status	What it describes	Why it changes or differs
4,294,967,296 possible addresses	Every value representable by a 32-bit IPv4 address	Fixed by the protocol: 2³²
Special-purpose space	Prefixes reserved for private use, loopback, shared addressing, documentation, multicast, and other defined purposes	The IETF and IANA registries define each prefix and its properties
Registered or allocated space	Resources recorded under IANA, RIR, legacy, provider, or organization administration	Registry status and delegated records can change
Globally routed space	Prefixes observed in the public routing system at a stated time	Announcements, withdrawals, filters, and route policy change continuously
Available supply	Resources that a registry, provider, holder, seller, or lessor can actually make available under current terms	Eligibility, authority, demand, policy, price, and live inventory all matter

How is the total number of IPv4 addresses calculated?

RFC 791 defines an IPv4 address as four octets, or 32 bits. Each bit has two values, so the number of combinations is:

2³² = 4,294,967,296

Dotted-decimal notation writes those bits as four numbers from 0 through 255. Each number represents one 8-bit octet, and 256 × 256 × 256 × 256 produces the same total. The dots make the value readable; they do not add address capacity.

How many addresses are in an IPv4 CIDR block?

A CIDR prefix length states how many of the 32 bits identify the network. The number of addresses in a prefix is 2^{32 − prefix length}. A shorter prefix contains more addresses; a longer prefix contains fewer.

Common IPv4 CIDR sizes and total address counts

Prefix	Total addresses	Common planning boundary
/8	16,777,216	Top-level or very large historical allocation scale
/12	1,048,576	Large private or provider planning block
/16	65,536	Large organization or site allocation boundary
/20	4,096	Mid-sized routed or internal block
/24	256	Common public routing and operational reference size
/28	16	Small subnet or provider-assigned range
/30	4	Traditional point-to-point subnet
/31	2	Two host addresses on supported point-to-point links under RFC 3021
/32	1	One exact IPv4 address or host route

These are total counts, not a promise of assignable hosts. The familiar “subtract two” rule applies to many traditional multi-access subnets because of network and broadcast addresses, but it is not universal: RFC 3021 permits both addresses on supported /31 point-to-point links, and a /32 identifies one exact address. Cloud, provider, anycast, gateway, and platform rules can reserve additional addresses.

How many IPv4 addresses are private or special-purpose?

RFC 1918 reserves three non-overlapping private-use blocks: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Together they contain exactly 17,891,328 private-use IPv4 addresses. Different organizations can reuse them because they are not globally reachable on the public Internet.

Private space is only one part of the special-purpose registry. Other prefixes support protocol, operational, testing, or documentation needs and have different source, destination, forwarding, and reachability properties.

Examples of IPv4 space that is not ordinary public unicast supply

Prefix	Purpose	Decision boundary
10.0.0.0/8	Private use	Reusable inside networks; not globally reachable
100.64.0.0/10	Shared address space	Commonly used between providers and subscribers; not ordinary public customer space
127.0.0.0/8	Loopback	Refers to the local host, not a remote public endpoint
169.254.0.0/16	Link-local	Applies on the local link and is not ordinary global unicast
192.0.2.0/24	Documentation TEST-NET-1	Safe for examples; not a prefix to deploy as real public service space
198.18.0.0/15	Benchmark testing	Reserved for controlled device or network testing
224.0.0.0/4	Multicast	Uses multicast semantics rather than ordinary unicast assignment
240.0.0.0/4	Reserved by protocol	Not ordinary public unicast supply

Use the current IANA IPv4 Special-Purpose Address Registry for an exact prefix. Do not derive a “usable public total” by subtracting a short hand-written list: entries and their properties are more specific than a single public-versus-private label.

How many public IPv4 addresses are left?

There is no single stable number that answers this question for every purpose. IANA's IPv4 Address Space Registry records the top-level status of each /8, while a separate recovered-space registry records returned resources and distributions. Each RIR applies its own current policy to recovered or limited pools. Existing registered resources may also be routed, idle, transferred, sold, or leased under different authority and eligibility conditions.

• Unallocated by IANA is a central registry status, not a count of addresses a business can order.
• Available from an RIR depends on the registry, policy, request type, waiting list or recovered pool, and observation date.
• Available in the transfer market requires a willing, authorized source and an eligible recipient under the applicable RIR process.
• Available to lease requires a verified right to grant use, routing authority, a suitable exact prefix, compatible terms, and live supply.
• Visible in BGP means a route was observed; it does not prove registry status, contractual authority, application acceptance, or market availability.

For a current decision, check the responsible RIR, the authoritative RDAP record, route and RPKI observations, and dated inventory. A search result that publishes one timeless “addresses left” figure collapses several different facts.

Why does IPv4 exhaustion still matter?

The mathematical total is fixed, but ordinary public IPv4 demand continues after the unrestricted central pool has been distributed. Networks keep operating through private addressing and NAT, carrier-grade NAT, transfers of eligible registered resources, time-limited leasing, provider assignments, address reclamation, and IPv6 deployment. These methods share or redistribute capacity; they do not create more IPv4 bit patterns.

IPv6 uses 128-bit addresses and therefore has 2¹²⁸ possible values. IPv6 deployment solves address-scale problems, but IPv4 and IPv6 are not directly interchangeable. A real plan may need dual stack, translation, or temporary IPv4 capacity while applications, users, peers, and security controls move.

Turn the address count into a network requirement

1. Count public endpoints and interfaces. Separate Internet-facing capacity from private addresses, internal segments, load balancers, gateways, failover, and temporary environments.
2. Choose the CIDR boundary. Include subnet design, upstream minimum prefix filters, aggregation, growth, reserve, and whether multiple smaller blocks are operationally acceptable.
3. Choose the access path. Compare a provider assignment, an RIR resource, an approved transfer or purchase, and a time-limited lease against the same duration and control requirements.
4. Verify the exact prefix. Check registry and contract authority, route origin, LOA where required, IRR objects, RPKI ROA, reverse DNS, geolocation, dated reputation evidence, and abuse contacts.
5. Price the whole lifecycle. Include setup, registry or transfer work, routing, support, term, renewal, monitoring, incident response, withdrawal, return, and renumbering.
6. Keep IPv6 in the design. Record which applications can use IPv6 now and which dependencies still require IPv4 so temporary capacity does not become an undocumented permanent assumption.

Use the IPv4 cost calculator after the prefix size is known. Then compare managed IPv4 leasing, buying IPv4 addresses, or current marketplace listings. Public inventory can change or be empty, and a listing is not proof of authority, routability, or application fit.

IPv4 address count FAQs

Primary standards and registries

• RFC 791: Internet Protocol and the 32-bit IPv4 address
• RFC 4632: Classless Inter-domain Routing
• RFC 1918: Private-use IPv4 address space
• RFC 3021: 31-bit prefixes on point-to-point links
• RFC 5737: IPv4 documentation ranges
• RFC 6598: Shared address space
• IANA IPv4 Address Space Registry
• IANA IPv4 Special-Purpose Address Registry
• IANA IPv4 Recovered Address Space Registry
• RFC 4291: IPv6 Addressing Architecture