IPv6 Calculator
Expand, compress and subnet an IPv6 address.
- Free
- No signup
- Nothing uploaded
- No watermark
- Compressed
- 2001:db8:85a3::8a2e:370:7334the canonical short form
- Expanded
- 2001:0db8:85a3:0000:0000:8a2e:0370:7334
- Prefix
- /64
- Network
- 2001:db8:85a3::/64
- First address
- 2001:db8:85a3::
- Last address
- 2001:db8:85a3:0:ffff:ffff:ffff:ffff
- Addresses in the block
- 2^64 (about 1.84e+19)
- Scope
- Documentation — reserved for examples, like 192.0.2.0/24 in IPv4
A /64 is the standard subnet size in IPv6. Anything longer breaks stateless address autoconfiguration.
How to Use the IPv6 Calculator Online
Expands, compresses and subnets an IPv6 address. Compression has exactly one rule that trips people up: the double colon may appear only once in an address, because two of them would make the number of omitted groups ambiguous. Expansion shows the full form so you can see what a compressed address actually says.
No software to install Free Works on any device
Step-by-Step Guide to Using the IPv6 Calculator
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1. Type an address, with a prefix or a mask
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2. Everything is worked out as you type — network, broadcast, range and host count
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3. It is pure arithmetic, so it works on private ranges and networks that do not exist yet
What is the IPv6 Calculator?
Expands, compresses and subnets an IPv6 address. Compression has exactly one rule that trips people up: the double colon may appear only once in an address, because two of them would make the number of omitted groups ambiguous. Expansion shows the full form so you can see what a compressed address actually says.
Why Use IP and Network Calculators?
Subnet masks, CIDR ranges and download times all come down to binary maths that is easy to slip on. These calculators do the sums in the page, so you can plan an address range or check a speed claim with confidence.
“One wrong subnet mask can take a whole office offline.”
- Subnets worked out instantly
- CIDR ranges made clear
- Download times estimated
- Browser details revealed
- Usable host counts shown
- IPv4 and IPv6 conversions
- MAC addresses checked
- No commands to install
Popular Uses for Subnet Calculators
Network jobs at home and at work often start with one of these sums.
- Planning an office network Split an address block into subnets for each floor, team or guest WiFi.
- Reading CIDR notation See the first address, last address and host count behind a range like /24.
- Download estimates Work out how long a large file will take on a given connection speed.
- Speed claims Turn megabits per second into megabytes to see what a plan really delivers.
- Device lookups Find the maker of a network card from its MAC address prefix.
- Browser checks See your user agent and browser details when a support team asks.
- WebSocket tests Connect to a WebSocket endpoint and watch messages go back and forth.
- IPv6 planning Convert an IPv4 address into IPv6 form while preparing a migration.
What You Can Do with the IPv6 Calculator
The calculation happens on your own machine, at your machine's speed
Shows the network, broadcast and usable host range together, which is the whole answer
Handles IPv6 at full length rather than truncating it for display
Why Use ToolXkit for IPv6 Calculator?
Your files stay with you
Everything runs inside your browser. Nothing you open or type is uploaded to a server.
Free, with no catch
No signup, no watermark and no daily limit on how often you use it.
Fast
Results appear in seconds, because nothing has to travel over the internet and back.
Works on any device
Use it on a computer, tablet or phone, in Chrome, Edge, Firefox or Safari.
Nothing to install
No app, no extension and no desktop program. Open the page and start.
Made for real people
Plain words and clear buttons, built by one developer who wanted tools like this to exist.
Network Tools for Different Users
Network administrators
Plan subnets, check CIDR ranges and size links for expected bandwidth.
Networking students
Practise subnetting for CCNA and other exams, and check answers quickly.
Developers
Test WebSocket servers, parse user agents and inspect TCP header fields.
IT support staff
Collect browser details and estimate transfer times while helping users.
Small office owners
Understand router settings and IP ranges without calling a technician every time.
Streamers and gamers
Check upload speed, latency and packet loss figures before a stream.
Best Times to Work Out a Subnet
Network calculators help when you are:
- Setting up a new router
- Studying for a networking exam
- Adding a guest WiFi network
- Estimating a large upload
- Comparing broadband plans
- Identifying an unknown device
- Moving to IPv6
- Debugging a WebSocket connection
Frequently Asked Questions
Answers to common questions about this tool.
Why can the double colon only appear once?
It stands for a run of zero groups, and the length of that run is inferred from how many groups are present. With two of them the split would be ambiguous — there would be no way to tell how many zeros belong to each — so the specification allows exactly one.
Why is a /64 the standard subnet size?
Because stateless address autoconfiguration assumes 64 bits of host portion. A subnet smaller than /64 breaks SLAAC, so even a point-to-point link between two routers conventionally gets a /64 — there is no shortage of addresses to conserve.
Is IPv6 Calculator accurate enough for real network work?
The maths behind addresses and ranges is exact, so the results match what a router expects. Double-check the input, especially the prefix length, since one wrong digit changes the whole range.
Do the calculators scan my network?
No. The subnet and speed calculators only work with the numbers you type in. They send no traffic into your network, and the only tool that connects anywhere is the WebSocket Tester, to the address you enter.
Why is my real download slower than the estimate?
The calculator assumes the full connection speed is available. In practice, WiFi, other devices, server limits and protocol overhead eat into it, so real downloads often take somewhat longer.
Is IPv6 Calculator free and private?
Yes. It costs nothing and needs no account. What you type stays in your browser and is never sent to ToolXkit, which matters when it describes a real company network.
What is the difference between Mbps and MBps?
Mbps means megabits per second, the unit broadband plans use. MBps means megabytes per second, the unit most download windows show. One byte is eight bits, so 100 Mbps is about 12.5 MBps.
Further reading
- RFC 4632: CIDR (IETF) The IETF standard for CIDR notation and how address blocks are divided.
- RFC 1918: Private address space (IETF) The ranges of private IP addresses meant for home and office networks.
- Number Resources (IANA) The body that hands out IP address blocks worldwide.
More Internet & Network Tools
Other free tools for the same kind of job.
- Bandwidth Calculator How much bandwidth your traffic actually needs, including the peak. Open tool
- Browser Information Checker Everything your browser reports about itself. Open tool
- CIDR Calculator Turn a CIDR prefix into a mask, a host count and a usable range. Open tool
- Data Transfer Calculator Work out transfer time for any size at any speed. Open tool
- Download Time Calculator How long a file really takes, with protocol overhead counted. Open tool
- Internet Speed Calculator Turn a connection speed into real download times. Open tool
- IP Range Calculator Find the first and last usable address in any block. Open tool
- IP to Binary Converter See an IPv4 address in binary, decimal, hex and octal. Open tool
- IP to Decimal Converter Convert an IPv4 address to its 32-bit integer form and back. Open tool