Quick start
- Enter an IPv4 address such as 192.168.1.10.
- Enter a CIDR prefix length from 0 to 32.
- Calculate to see mask, wildcard, network, broadcast, and usable range.
Best uses
Start here if one of these sounds like your job. The examples below show which inputs matter most.
- Find the network and broadcast address for an IPv4 CIDR block.
- Convert a prefix length such as /24 into a dotted decimal subnet mask.
- Check usable host range and address count.
- Practice subnetting for networking, security, or developer work.
What this calculator is solving
The Subnet Calculator helps developers, students, and network learners check IPv4 CIDR blocks without doing every binary step by hand.
Match each input label on the calculator to the real measurement, amount, rate, unit, or setting for your job.
The formula in plain language
In plain language: The calculator converts IPv4 octets to a 32-bit number, builds the CIDR subnet mask, then uses bitwise network and wildcard math. The examples on the page are there so you can compare your inputs with a filled-out example before copying the answer.
The example cards on the calculator page show a complete set of inputs and the kind of answer you should expect.
How to read the answer
Read the main result first. Then check the smaller lines for the totals, units, ranges, counts, or formula steps behind it.
- Network address is the first address in the CIDR block.
- Broadcast address is the last address in normal IPv4 subnet notation.
- Usable range excludes network and broadcast except for /31 and /32 style cases.
Common mistakes to avoid
If the answer looks strange, the most likely cause is a small input mismatch: a mixed unit, copied value, wrong mode, missing label, or result used for the wrong job.
- Do not use this for IPv6 subnetting.
- Do not assume the calculator changes any live network setting.
- Check your router, cloud provider, or firewall rules before applying subnet plans.
Research and references
These references help check the measurements, units, limits, or safety notes used in this guide.
Worked examples for Subnet Calculator
Network 192.168.1.0, usable 192.168.1.1-192.168.1.254
16 total addresses
2 usable /31 addresses
FAQ in plain language
When should I use the Subnet Calculator?
Use it when your task matches one of these common needs: Find the network and broadcast address for an IPv4 CIDR block. Convert a prefix length such as /24 into a dotted decimal subnet mask. It works best when you already know the text, code, URL, mode, format, or technical setting the page asks for.
What is the Subnet Calculator doing with my inputs?
In plain language: The calculator converts IPv4 octets to a 32-bit number, builds the CIDR subnet mask, then uses bitwise network and wildcard math. The examples on the page are there so you can compare your inputs with a filled-out example before copying the answer.
What do the main Subnet Calculator inputs mean?
The main inputs are usually text, code, a URL, a number base, or a mode setting. Paste only the part you want the tool to work on and compare the output with the examples.
How should I read the Subnet Calculator answer?
Read the output next to your original input. If the tool changes format, units, encoding, spacing, or capitalization, compare a small sample before copying the whole result into another app.
What should I double-check before trusting the answer?
This tool covers IPv4 CIDR math. It does not configure routers, validate a live network, or handle IPv6 subnets. Also check the selected mode, input format, encoding, and whether the text includes private keys, passwords, or sensitive data.
Why do /31 and /32 subnets look different?
Most IPv4 subnets reserve the first address as the network address and the last address as broadcast. A /31 is commonly used for point-to-point links with two usable addresses, and a /32 represents one exact host address.
Can this calculator choose the best subnet size for me?
It shows the math for one IPv4 CIDR block, but it does not design the network. Pick a prefix after you know the device count, growth room, provider-reserved addresses, routing rules, firewall rules, and whether the environment treats network and broadcast addresses normally.
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Keep exploring
If this guide is close but not exact, these links keep you near the same kind of problem.
- Developer Tools Browse the full category for related tools that help with the same job.
- All free tools Search the complete Access Free Tools library by task, category, or tool name.
- All calculator and utility guides Find more plain-language examples, formulas, mistakes, and result explanations.
- Free calculator resources Start here when you are not sure which calculator page fits.
Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to save the inputs and result in notes, homework, a message, or a project list. Check the units, labels, and limits before copying.