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IP Range CalculatorPRO
IPv4 Subnetting & RangeInstant Client-Side Tool

Network Bits Calculator

Identify the network prefix length.

Network Bits Calculator: inputs and results

Enter an IP address, CIDR prefix, or range. Then check its first and last address below.

Quick presets:

Calculated Boundaries & ParametersReady

Network Address192.168.1.0
Broadcast Address192.168.1.255
First Usable Host192.168.1.1
Last Usable Host192.168.1.254
Subnet Mask255.255.255.0
Wildcard Mask0.0.0.255
Total Addresses256
Usable Host Range254

Key Capabilities

  • •100% Client-Side: Zero telemetry or server latency.
  • •RFC Compliant: Exact 32-bit and 128-bit integer precision.
  • •Quick Copy: Instant access to CIDR, mask, and range bounds.
  • •Cross-Platform: Works on desktop, tablet, and mobile browsers.
Open Full Interactive Suite

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How Network Bits Calculator Works?

This tool works by counting the consecutive 1 bits in a subnet mask, from left to right. That count is the prefix length.

  1. Enter a subnet mask

    Type a dotted mask such as 255.255.240.0.

  2. Convert each octet to binary

    255 = 11111111, 240 = 11110000, and 0 = 00000000.

  3. Count the 1 bits

    8 + 8 + 4 + 0 = 20 network bits.

  4. Return the prefix

    The result is /20, with 12 bits left for hosts.

Network Bits Calculator Formula

The formula is Network Bits = the sum of the 1 bits in all 4 mask octets.

Network bits

n = popcount(o1) + popcount(o2) + popcount(o3) + popcount(o4)

popcount counts the 1 bits in one octet.

Octet values

0, 128, 192, 224, 240, 248, 252, 254, 255

A valid mask octet takes 1 of these 9 values, holding 0 to 8 network bits.

Network bits from host count

n = 32 − log2(Total)

A block of 4,096 addresses has 32 − 12 = 20 network bits.

Worked example: 255.255.240.0

255 → 11111111 → 8 bits
255 → 11111111 → 8 bits
240 → 11110000 → 4 bits
0   → 00000000 → 0 bits
Network bits = 20 → /20

Network Bits Calculator Conversion Table

The table maps 12 dotted subnet masks to their binary form and network bit count.

Subnet MaskBinary MaskNetwork BitsNetwork Bytes
255.0.0.011111111.00000000.00000000.0000000081
255.240.0.011111111.11110000.00000000.00000000121.5
255.255.0.011111111.11111111.00000000.00000000162
255.255.224.011111111.11111111.11100000.00000000192.375
255.255.240.011111111.11111111.11110000.00000000202.5
255.255.248.011111111.11111111.11111000.00000000212.625
255.255.252.011111111.11111111.11111100.00000000222.75
255.255.255.011111111.11111111.11111111.00000000243
255.255.255.19211111111.11111111.11111111.11000000263.25
255.255.255.24011111111.11111111.11111111.11110000283.5
255.255.255.25211111111.11111111.11111111.11111100303.75
255.255.255.25511111111.11111111.11111111.11111111324

What is Network Bits Calculator?

The Network Bits Calculator is a tool that returns how many bits of a subnet mask identify the network. The network bit count equals the CIDR prefix length.

Every IPv4 subnet mask starts with a run of 1 bits and ends with a run of 0 bits. The 1 bits mark the network part of the address. The Network Bits Calculator counts that run and reports it as a number from 0 to 32.

Network bits and prefix length describe the same value. 255.255.255.0 has 24 network bits, which is written as /24 in CIDR notation.

What are the uses of Network Bits Calculator?

There are 4 main uses of the Network Bits Calculator, including mask translation, configuration review, and exam practice.

  • Translating legacy configurations

    Older devices show dotted masks, and newer platforms expect a prefix length. The bit count bridges both formats.

  • Reviewing configuration files

    Auditors scan configurations for masks such as 255.255.248.0 and confirm that each one equals /21.

  • Practicing mask conversion

    Students convert dotted masks to prefix lengths without a calculator and check the answer with the tool.

  • Matching route prefixes

    Routing tables compare prefix lengths. The bit count shows which route is more specific.