Network calculators for people who configure networks
Eight focused tools for subnetting, address planning, link sizing and encapsulation. Each one shows the formula behind the result, states its assumptions, and covers the edge cases that a naive implementation gets wrong — /31 point-to-point links, 128-bit IPv6 arithmetic, variable-length header stacks and byte-versus-bit unit confusion.
Every calculation runs in your browser. No address or network detail you enter is uploaded anywhere.
The eight calculators
- IPv4 Subnet CalculatorWork out the network address, broadcast address, usable host range and binary form of any IPv4 subnet in CIDR notation.Open calculator →
- CIDR CalculatorConvert between CIDR prefix lengths, subnet masks and wildcard masks, with a full /0 to /32 reference table.Open calculator →
- IPv6 CalculatorExpand, compress and analyse IPv6 addresses and prefixes using exact 128-bit arithmetic.Open calculator →
- VLSM PlannerAllocate variable length subnet masks from a host requirement list, largest subnet first, with wasted-address accounting.Open calculator →
- IP ConverterConvert IPv4 and IPv6 addresses between dotted-decimal, binary, hexadecimal and decimal integer formats.Open calculator →
- Bandwidth CalculatorCalculate transfer time for a file size and link speed, or the bandwidth required to hit a target transfer window.Open calculator →
- TCP Throughput CalculatorCompute the bandwidth-delay product, window-limited throughput and the TCP window size needed to fill a link.Open calculator →
- MTU / MSS CalculatorModel encapsulation overhead layer by layer — Ethernet, IPv4, IPv6, GRE, VXLAN, GTP-U, PPPoE, IPsec — and derive TCP MSS.Open calculator →
What makes these different
Correct edge cases
RFC 3021 /31 links carry two usable addresses, not zero. /0 needs 64-bit arithmetic because 232 overflows a signed integer. Both are handled.
Exact IPv6 maths
128-bit values are held in BigInt, so a /64 returns 18,446,744,073,709,551,616 rather than a number rounded to 15 significant figures.
Visible assumptions
The MTU calculator shows every header size with its RFC, and the TCP calculator states that its results are theoretical bounds rather than predictions.
Nothing leaves your browser
These are static pages with no backend. There is no database, no logging of inputs and no API call when you press Calculate.
Conversion tools
Single-purpose pages for the conversions people search for most.
- IP to Binary ConverterConvert an IPv4 address to its 32-bit binary representation with octet separation.
- Binary to IP ConverterTurn a 32-bit binary string back into a dotted-decimal IPv4 address.
- IP to Hex ConverterConvert an IPv4 address to its 8-digit hexadecimal form.
- Hex to IP ConverterTurn an 8-digit hexadecimal value back into a dotted-decimal IPv4 address.
- IP to Decimal ConverterConvert an IPv4 address to its 32-bit unsigned decimal integer.
- Decimal to IP ConverterTurn a 32-bit decimal integer back into a dotted-decimal IPv4 address.
- Mbps to MB/s ConverterConvert megabits per second to megabytes per second and back, with the exact 8:1 bit-to-byte relationship shown.
- MB/s to Mbps ConverterConvert megabytes per second to megabits per second for link-speed comparisons.
- Gbps to MB/s ConverterConvert gigabits per second to megabytes per second for storage and network planning.
Guides
The theory behind the calculators, with worked arithmetic.
- Subnetting guideHow subnet masks, block sizes and host ranges work, with the exact arithmetic worked through by hand.
- IPv6 address typesGlobal unicast, link-local, unique local, multicast and the transition prefixes, with their allocation ranges.
- CIDR notation explainedWhy classless addressing replaced classful networking and how prefix lengths map onto masks.
- VLSM design guideSizing subnets from host requirements, reserving growth space and avoiding the classic VLSM ordering mistakes.
- MTU, MSS and encapsulation overheadWhy tunnels break TCP, how PMTUD works, and how to size MSS for GRE, VXLAN and GTP-U paths.
- TCP throughput and the BDPBandwidth-delay product, window scaling and why a fast long-distance link underperforms without tuning.
Which tool should I use?
| If you need to… | Use |
|---|---|
| Check the network address, broadcast and host range of one subnet | IPv4 Subnet Calculator |
| Convert a prefix length to a mask, or look up what a /27 means | CIDR Calculator |
| Split a block across many VLANs or sites of different sizes | VLSM Planner |
| Design IPv6 addressing, or work out what an address actually is | IPv6 Calculator |
| Turn a decimal or hex value from a log into an address | IP Converter |
| Size a link for a backup window, or estimate a transfer time | Bandwidth Calculator |
| Explain why a fast link is underperforming | TCP Throughput Calculator |
| Work out tunnel overhead or the MSS to configure | MTU / MSS Calculator |