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IPv4 Subnet and CIDR Calculator

Calculate IPv4 network address, broadcast, usable host range, netmask, wildcard, binary mask, and RFC address type (RFC 1918, /31, CGNAT).

Input Parameters

Try Example:

Accepts 192.168.1.10/24, 192.168.1.10 255.255.255.0, or 192.168.1.10 0.0.0.255.

032

Used when the IP field above does not include an inline /prefix or mask.

Calculation Results

Prefix /24 Bit Allocation (32-bit Address Space)
Network: 24 bit (75%)Host: 8 bit (25%)
IP Address
192.168.1.10
CIDR Prefix
24 bits
CIDR Notation
192.168.1.0/24
Network Address
192.168.1.0
Broadcast Address
192.168.1.255
First Usable Host
192.168.1.1
Last Usable Host
192.168.1.254
Usable Hosts
254 Hosts
Total IP Addresses
256 Addresses
Subnet Mask
255.255.255.0
Wildcard Mask
0.0.0.255
Binary Mask
11111111.11111111.11111111.00000000
Binary IP
11000000.10101000.00000001.00001010
IP Address Type
Private (RFC 1918)
IP Class
C
Hexadecimal IP
0xC0A8010A
Reverse DNS (in-addr.arpa)
1.168.192.in-addr.arpa
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CIDR Quick Reference Table (/0 to /32)
CIDRNetmaskWildcardUsable Hosts
/00.0.0.0255.255.255.2554,294,967,294
/1128.0.0.0127.255.255.2552,147,483,646
/2192.0.0.063.255.255.2551,073,741,822
/3224.0.0.031.255.255.255536,870,910
/4240.0.0.015.255.255.255268,435,454
/5248.0.0.07.255.255.255134,217,726
/6252.0.0.03.255.255.25567,108,862
/7254.0.0.01.255.255.25533,554,430
/8255.0.0.00.255.255.25516,777,214
/9255.128.0.00.127.255.2558,388,606
/10255.192.0.00.63.255.2554,194,302
/11255.224.0.00.31.255.2552,097,150
/12255.240.0.00.15.255.2551,048,574
/13255.248.0.00.7.255.255524,286
/14255.252.0.00.3.255.255262,142
/15255.254.0.00.1.255.255131,070
/16255.255.0.00.0.255.25565,534
/17255.255.128.00.0.127.25532,766
/18255.255.192.00.0.63.25516,382
/19255.255.224.00.0.31.2558,190
/20255.255.240.00.0.15.2554,094
/21255.255.248.00.0.7.2552,046
/22255.255.252.00.0.3.2551,022
/23255.255.254.00.0.1.255510
/24255.255.255.00.0.0.255254
/25255.255.255.1280.0.0.127126
/26255.255.255.1920.0.0.6362
/27255.255.255.2240.0.0.3130
/28255.255.255.2400.0.0.1514
/29255.255.255.2480.0.0.76
/30255.255.255.2520.0.0.32
/31255.255.255.2540.0.0.12
/32255.255.255.2550.0.0.01
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Visual Network Topology Generator (SVG / PNG)

Network Architecture & Subnet Allocation (192.168.1.0/24)KalkuNet.com • Auto-TopologyISP / Upstream BackboneBGP / Default Route 0.0.0.RTRCore Router / L3 FirewallPrefix 192.168.1.0/24 • Mask 255SWManaged L2/L3 Distribution VLAN Trunking & Spanning Tree (RGateway / First Host192.168.1.1[VLAN Gateway]Active Host Pool254 Usable Endpoint[192.168.1.0/24]Broadcast / Boundary192.168.1.254[255.255.255.0]
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Technical Accuracy Note: Calculation results are engineering estimates based on standard RFC/IEEE/ITU-T models. Actual field performance may vary due to protocol overhead, hardware specifications, and environmental factors.

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How to Use This Tool

  1. Enter an IPv4 address in the input field using CIDR notation (e.g. 192.168.1.10/24), IP with netmask (192.168.1.10 255.255.255.0), IP with wildcard mask (192.168.1.10 0.0.0.255), or enter a bare IP and select a prefix length from /0 to /32.
  2. Review the instant calculation results including Network Address, Broadcast Address, First and Last Usable Host range, Usable Host Count, Netmask, Wildcard Mask, binary mask representation, and RFC address classification.
  3. Use the Copy buttons, export to Markdown or CSV, or expand the CIDR Quick Reference Table (/0 to /32) to compare adjacent subnet block sizes.

Worked Example: Office LAN /24 (192.168.1.10/24)

For input 192.168.1.10/24, a bitwise AND with netmask 255.255.255.0 produces network address 192.168.1.0 and broadcast address 192.168.1.255 (wildcard 0.0.0.255). Out of 256 total addresses (2^8), there are 254 usable host addresses ranging from 192.168.1.1 to 192.168.1.254 classified as Private (RFC 1918).

Example Input
IPv4 Address (or IP/CIDR, IP + Netmask, IP + Wildcard)
192.168.1.10
CIDR Prefix (/0 – /32)
24 bits
Calculated Output
IP Address
192.168.1.10
CIDR Prefix
24 bits
CIDR Notation
192.168.1.0/24
Network Address
192.168.1.0
Broadcast Address
192.168.1.255
First Usable Host
192.168.1.1
Last Usable Host
192.168.1.254
Usable Hosts
254 Hosts
Total IP Addresses
256 Addresses
Subnet Mask
255.255.255.0
Wildcard Mask
0.0.0.255
Binary Mask
11111111.11111111.11111111.00000000
Binary IP
11000000.10101000.00000001.00001010
IP Address Type
Private (RFC 1918)
IP Class
C
Hexadecimal IP
0xC0A8010A
Reverse DNS (in-addr.arpa)
1.168.192.in-addr.arpa

Core Concept & Engineering Notes

IPv4 subnetting and Classless Inter-Domain Routing (CIDR) calculation form the foundation of modern IP network design and routing architecture. Every IPv4 address consists of 32 bits written as four dotted-decimal octets ranging from 0.0.0.0 to 255.255.255.255. A CIDR prefix length such as /24 specifies how many leading bits from the left identify the network segment, while the remaining trailing bits (32 minus the prefix length) identify individual host interfaces within that broadcast domain. This calculator determines the network address using a bitwise AND operation between the IPv4 address and the netmask, and computes the broadcast address using a bitwise OR between the network address and the wildcard mask. For standard prefixes from /0 through /30, two addresses are reserved in every block—the first address identifies the network itself and the last address serves as the directed broadcast address—leaving two to the power of the host bits minus two usable host addresses. Special handling applies to /31 point-to-point router links defined in RFC 3021, which provide two usable addresses with no broadcast waste, and /32 host routes, which lock onto a single interface address. Common operational mistakes include sizing a VLAN subnet too tightly without room for future DHCP growth, inverting netmasks and wildcard masks when configuring OSPF network statements or firewall access control lists, and overlapping RFC 1918 private ranges across VPN tunnels. Inspecting the exact network boundary, usable host range, binary mask structure, and RFC address classification helps network engineers prevent routing overlaps and interface misconfigurations before deploying changes to production switches and routers.

How It Was Calculated (Formulas & Steps)

Frequently Asked Questions (FAQ)

Why does a /24 subnet have 254 usable hosts instead of 256?

A /24 subnet leaves 8 host bits, yielding 2^8 = 256 total addresses. However, the first address (e.g. 192.168.1.0) is reserved as the Network ID and the last address (192.168.1.255) is reserved as the Broadcast Address, leaving 254 assignable host addresses.

When should I use a /30 vs a /31 prefix for point-to-point router links?

A /30 prefix allocates 4 total addresses (2 usable hosts) and works with all legacy equipment. A /31 prefix (RFC 3021) saves 50% of IPv4 space by providing 2 usable point-to-point addresses with no broadcast address, and is supported by virtually all modern routers.

What is the difference between a Subnet Mask and a Wildcard Mask?

A subnet mask uses binary 1s to mark network bits and 0s for host bits (e.g. /24 = 255.255.255.0). A wildcard mask is the bitwise inverse (NOT) of the subnet mask (e.g. /24 = 0.0.0.255) and is commonly used in OSPF network statements and router ACLs.

What is the CGNAT 100.64.0.0/10 (RFC 6598) address range?

The 100.64.0.0/10 block (100.64.0.0 through 100.127.255.255) is reserved by IANA under RFC 6598 specifically for Carrier-Grade NAT (Shared Address Space) between service provider cores and customer premises equipment so it does not collide with customer RFC 1918 LANs.

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References & Notes

Last updated: Technically Verified · Industry Standard

Note: Results above are mathematical estimates based on standard formulas. Always verify against official vendor documentation and site conditions before production deployment.

🔗Related Scenarios & Companion Calculators

Browse All 30+ Scenarios →

⚡ Ready-to-Use Scenario Presets:

/32 = Mask 255.255.255.255 • 1 Usable Hosts→
/32 Subnet Mask (255.255.255.255): Usable Hosts (1), Wildcard & IPv4 Range

Instant /32 CIDR reference: Subnet Mask is 255.255.255.255, Wildcard 0.0.0.0, Total IPs 1, and 1 Usable Hosts. Ideal for OSPF/BGP Router Loopback & Single Host Route.

/30 = Mask 255.255.255.252 • 2 Usable Hosts→
/30 Subnet Mask (255.255.255.252): Usable Hosts (2), Wildcard & IPv4 Range

Instant /30 CIDR reference: Subnet Mask is 255.255.255.252, Wildcard 0.0.0.3, Total IPs 4, and 2 Usable Hosts. Ideal for Point-to-Point Inter-Router WAN Link (2 Usable IPs).

/29 = Mask 255.255.255.248 • 6 Usable Hosts→
/29 Subnet Mask (255.255.255.248): Usable Hosts (6), Wildcard & IPv4 Range

Instant /29 CIDR reference: Subnet Mask is 255.255.255.248, Wildcard 0.0.0.7, Total IPs 8, and 6 Usable Hosts. Ideal for DMZ Public Server Sub-Block & BGP Peering (6 Hosts).

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MikroTik Bandwidth Calculator (Simple Queue, Burst, PCQ, FQ-CoDel)

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🔬 Scientific Methodology & Normative Verification

Engineering Sensitivity Analysis, Response Curve & Technical Citation

✓ Calibrated to ISO/IEC/IEEE/TIA Clauses

1. 1. 3-Point Engineering Sensitivity & Tolerance Envelope

Comparative evaluation across theoretical laboratory bounds (0% loss), current nominal operating point, and conservative field safety bounds (±15% thermal/aging derating).

Evaluated Parameter Ideal Theoretical Bound Nominal Operating Point Conservative Safety Bound (±15%) Engineering Derating Rule
CIDR Prefix 21.6 24 27.6 Engineering Safety Margin (+15% Overhead)
Usable Hosts 274 254 216 Thermal & Aging Derating (-15% Worst-Case)
Total IP Addresses 230 256 294 Engineering Safety Margin (+15% Overhead)

2. 2. Mathematical Function Curve & Operating Coordinate (x₀, y₀)

MATHEMATICAL RESPONSE CURVE: CIDR PREFIX VS CIDR PREFIX Conservative Engineering Bound (+15% Safety Margin) 9.6 14.4 19.2 24 28.8 33.6 38.4 (x₀=24, y₀=24) Variabel Independen (x): CIDR Prefix

3. 3. Physical Constants & Normative Standard Clauses

R_loop(Cat6, 20°C) = 14 Ω/100m ANSI/TIA-568.2-D & IEEE 802.3bt

DC Loop Resistance for 23 AWG Solid Copper Cat6

Clause 6.4.1 / Table 145-1 — Nominal 23 AWG solid copper loop resistance at 20°C is 14.0 Ω/100m (TIA maximum ceiling is 18.8 Ω/100m).

α_opt(1490nm) = 0.25 dB/km ITU-T Rec. G.652.D & G.984.2

Single-Mode Optical Fiber Attenuation Coefficient at 1490 nm

Table 1 / Class B+ & C+ Optical Path — Typical G.652.D attenuation at 1490 nm downstream is 0.22–0.25 dB/km (1310 nm upstream: 0.35 dB/km).

α_Cu(20°C) = 0.00393 °C⁻¹ IEC 60028

Temperature Coefficient of Resistance for Copper

International Annealed Copper Standard — Used in thermal derating equation: R(T) = R_20 × [1 + 0.00393 × (T - 20)].

4. 4. Independent Technical & Academic Citation (IEEE / APA 7th / BibTeX / LaTeX)

Use the standard citation formats below to reference this computational methodology in engineering specifications, audit reports, or academic papers.

Format IEEE & APA 7th Edition

[IEEE] KalkuNet Engineering Team, "IPv4 Subnet and CIDR Calculator — Standard Engineering Computational Instrument," KalkuNet Technical Suite, 2026. [Online]. Available: https://kalkunet.com/en/tools/subnet-calculator. [Accessed: 2026-11-08].

[APA 7th] KalkuNet Engineering Team. (2026). IPv4 Subnet and CIDR Calculator (Production release 2026-11-08) [Engineering computational software]. KalkuNet. https://kalkunet.com/en/tools/subnet-calculator

BibTeX & LaTeX Derivation Snippet
@software{kalkunet_subnet_calculator_2026,
  author = {{KalkuNet Engineering Team}},
  title = {{IPv4 Subnet and CIDR Calculator --- KalkuNet Engineering Suite}},
  year = {2026},
  publisher = {KalkuNet.com},
  url = {https://kalkunet.com/en/tools/subnet-calculator},
  urldate = {2026-11-08}
}

% LaTeX Engineering Derivation — Generated via https://kalkunet.com/en/tools/subnet-calculator
\begin{equation}
  \text{Model: } Network Address = IP Address AND Subnet Mask
\end{equation}
% Parameter Input Terukur: ip = 192.168.1.10, \; prefix = 24
% Hasil Evaluasi Numerik : ip = \mathbf{192.168.1.10}, \; prefix = \mathbf{24}, \; cidr = \mathbf{192.168.1.0/24}