Next or previous IP address calculator

Enter a canonical dotted-decimal address, choose a direction, and receive the adjacent address plus its unsigned integer value. The calculation handles every byte boundary correctly, so moving forward from an address ending in 255 carries into the octet on its left, while moving backward from an address ending in 0 borrows across that boundary. It is useful for subnet planning, configuration reviews, test fixtures, and scripts that must avoid error-prone manual arithmetic.

Convert an IPv4 address without manual octet arithmetic

An IPv4 address is usually written as four decimal octets separated by periods, but underneath that notation it is one unsigned 32-bit integer. This calculator parses the four octets, combines them into that integer, adds or subtracts exactly one, and converts the result back to dotted-decimal form. Thinking in terms of one integer is what makes rollover reliable. For example, the address 192.168.0.255 is not followed by an impossible last octet of 256; it is followed by 192.168.1.0. In the other direction, the address before 10.0.1.0 is 10.0.0.255. Supply the address in canonical form with exactly four octets, choose next or previous, and use the returned result address directly. The response also includes the resulting unsigned integer value, which is convenient when comparing addresses, sorting fixtures, or checking another implementation. No subnet mask is required because the operation concerns adjacency across the complete IPv4 address space rather than membership within a particular network block.

Understand rollover, borrowing, and address-space limits

Each IPv4 octet ranges from 0 through 255. When incrementing, a final octet below 255 simply increases by one. At 255, that octet becomes 0 and a carry moves left; the carry can cross several byte boundaries, as in 10.255.255.255 becoming 11.0.0.0. Decrementing applies the reverse rule. A zero octet becomes 255 while one is borrowed from the octet to its left, so 172.16.0.0 becomes 172.15.255.255. The calculator performs these transitions through integer arithmetic instead of a chain of special cases. It also rejects movement beyond the finite IPv4 range. There is no next value after 255.255.255.255, and there is no previous value before 0.0.0.0. Those requests return a clear input error instead of wrapping around, because silent wraparound could turn a boundary check into a completely different address. The tool treats all syntactically valid IPv4 values consistently, including addresses commonly reserved for networks, broadcasts, loopback, private use, or documentation.

Use strict input rules for predictable automation

The input contract deliberately accepts canonical dotted-decimal IPv4 notation only. An address must contain exactly four decimal octets, each between 0 and 255. Signs, surrounding spaces, missing octets, and leading zeros are rejected. Rejecting leading zeros avoids ambiguity with software that historically interpreted such components as octal numbers, while strict component counts prevent shortened forms from acquiring environment-dependent meanings. The direction is a finite choice: next or previous, with next used when the field is omitted. Because the algorithm uses no network calls, random values, clocks, or external state, the same input always produces the same output in the browser and through the API. That determinism makes the capability suitable for infrastructure scripts, IP address management exports, unit tests, and repeatable documentation examples. It does not determine whether the resulting address is assignable in a specific subnet; apply your subnet mask, allocation policy, and reserved-address rules separately. The API price is $0.002 per request, while the browser calculation can run locally on this page.