SeaMeWe4 Net Tools is an independent set of free, browser-based networking calculators — subnet and CIDR math, IPv6 addressing, VLSM planning, AWS/Azure VPC sizing, and fiber-latency estimates — built for network engineers, students and cloud teams who need a fast, accurate answer without signing up or installing anything.
What the calculators do
- Subnet Calculator (home page) — IPv4 network, broadcast, host range and mask math from an IP address and prefix.
- IP Subnet Calculator — finds the subnet that contains a single IP address, plus its neighboring addresses.
- CIDR Calculator — converts between CIDR notation, IP ranges and supernetted blocks.
- IPv6 Subnet Calculator — expands, compresses and subdivides 128-bit IPv6 prefixes.
- VLSM Calculator — splits one network into differently sized subnets by host count.
- AWS/Azure VPC Subnet Calculator — usable IPs per subnet after each cloud provider’s reserved addresses.
- Network Latency Calculator — best-case fiber latency between cities, plus a file-transfer-time estimate.
What we do not do
SeaMeWe4 Net Tools does not scan, probe or monitor any third-party network, host or IP address you enter — every calculation happens in your browser using the numbers you type, not a live lookup against the internet. We do not publish outage, uptime or performance claims about any real network, submarine cable system or cloud provider. We are not the SEA-ME-WE 4 consortium or any of its member operators, and we are not Amazon Web Services, Microsoft Azure, or any other company named on this site — this is an independent educational project.
How results are checked
Each calculator is checked against a fixed set of worked inputs — including edge cases such as /0, /31, /32 and IPv6 ::1 — before it is published, and the browser-side math mirrors the same formulas used to generate those worked examples. Where a rule or number comes from an external standard, we cite it: IPv4 subnetting follows RFC 950, variable-length subnetting follows RFC 1878, IPv6 addressing follows RFC 4291, and CIDR notation follows RFC 4632 — each checked against the current text on rfc-editor.org as of 25 Oct 2026.
Updates and corrections
This page and the calculators it describes are reviewed periodically. If you find a wrong number, a broken edge case, or a source that has since changed, use the Contact page — we check every report and correct confirmed errors. Last reviewed: 25 Oct 2026.
Frequently asked questions
Is SeaMeWe4 Net Tools affiliated with the SEA-ME-WE 4 cable system?
No. The name references the real submarine cable system for context on our latency calculator; this site is an independent educational project, not affiliated with, endorsed by or operated for that consortium or any operator.
Do the calculators send my data anywhere?
No. Every calculator runs entirely in your browser; the IP addresses, prefixes or file sizes you enter are never transmitted to or stored on our server.
How do I report a wrong result?
Use the Contact page and include the exact input you used. We test every calculator against fixed example inputs and will check any input that produces an unexpected result.
Who runs this site
SeaMeWe4 Net Tools is maintained by an independent editorial team. We are not a registered network operator or cable consortium, and the figures and tools here are for learning and planning, not a managed network service. See our Privacy Policy and Terms of Use for how the site itself handles data and usage.
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