New · Version 2.5: designed for iPhone Duo

The complete network toolkit
for iPhone, iPad & iPhone Duo

IPv4 & IPv6 subnet calculator, TLS certificate checks, DNS lookup, ping, traceroute, VLSM designer, and email authentication in one fast, native app for iPhone, iPhone Duo, iPad and Mac. Live results as you type, synced across your devices.

🛡️ Trusted by network engineers since 2013, on the App Store for over a decade.
Download on the App Store Try the free web calculator →
★★★★★ 4.7
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Subnet Plus on iPhone Duo unfolded: Calculate with the binary mask picker on the wide inner display Unfolded
Subnet Plus on iPhone Duo folded: Calculate on the outer display

iPhone Duo, folded and unfolded. Shown: Calculate with the new binary mask picker.

New in 2.5

Made for iPhone Duo. Sharper on every iPhone.

SubnetPlus fills both the outer and inner displays of iPhone Duo and adapts instantly as you fold and unfold, with tabs, results and ads laid out for each screen. Calculate gets a new binary mask picker: step the prefix and watch the network and host bits shift, color-coded, with the dotted-decimal mask right underneath. And the new TLS Certificate tool checks any host and port for expiry, chain problems, hostname mismatches, weak keys and legacy TLS.

iPhone Duo: outer and inner displays, adapts as you fold Binary mask picker: network and host bits, color-coded TLS Certificate: expiry, chain, names, TLS version and cipher Certificate watchlist: reminders 30, 14, 7 and 1 days out (Pro) Expiry widget: Home Screen and Lock Screen (Pro) Siri: "Check a certificate with SubnetPlus"
Get version 2.5 free
The binary mask picker: 192.168.1.0/24 shown as 24 blue network bits and 8 orange host bits above 255.255.255.0
The new binary mask picker in Calculate

iPhone and iPad

Native on iPhone and iPad, too

iPhone

Live results as you type, a tab bar within thumb’s reach, Home Screen and Lock Screen widgets, Live Activities in the Dynamic Island, and Siri.

Subnet Plus on iPhone: Calculate with the binary mask picker Subnet Plus on iPhone: TLS certificate check

iPad

A full iPadOS layout with a sidebar for Calculate, Tools, History and Library, and every result on one screen. Your saved work syncs from iPhone through iCloud.

Subnet Plus on iPad: Calculate with the sidebar layout
2013
On the App Store since
4.7★
App Store rating
45
Languages supported
20+
Networking tools

Free · Right in your browser

Try the online Subnet Calculator

IPv4 & IPv6 subnetting, VLSM planning, and mask conversion. Instant results, no download or signup required.

Open the Web Calculator →

Features

One app for everything networking

🔢

IPv4 & IPv6 Subnet Calculator

Network and broadcast addresses, usable host ranges, masks, wildcard, and host counts, calculated live as you type any CIDR. The new binary mask picker shows network and host bits change as you step the prefix.

🔐

TLS CertificateNew

Check the certificate on any host and port: days until expiry, the names it covers, the full chain, TLS version and cipher. Works on VPN gateways, load balancers, LDAPS and mail servers. Pro adds a watchlist with expiry reminders and a widget.

✉️

Email Authentication

Check any domain's SPF, DKIM, and DMARC records at a glance. Diagnose deliverability and catch misconfigurations in seconds.

🔎

DNS Lookup

Resolve A, AAAA, MX, TXT, and more records for any hostname with one tap. Large DNSSEC and long TXT responses load in full, with no truncation.

📡

Ping & Traceroute

Measure ICMP round-trip time and packet loss, and trace the full network path hop-by-hop to any host.

🧩

VLSM Designer

Carve a network into right-sized subnets with variable-length masks. Plan addressing without spreadsheets.

🔄

Mask, Supernet & Aggregate

Convert CIDR ↔ mask ↔ wildcard, summarize many networks into one, turn IP ranges into minimal CIDR blocks, and check subnet membership.

☁️

Save & Sync with iCloud

Build a library of your most-used subnets, plans, and lookups, with full history, synced privately across all your devices.

Subnet Calculator TLS Certificate Email Auth (SPF/DKIM/DMARC) DNS Lookup Ping Traceroute VLSM Designer Mask Converter Subnet Membership Range → CIDR Supernet / Aggregate CIDR Cheat Sheet

A closer look

Built for the way you work

Traceroute on iPhone DNS lookup on iPhone Certificate watchlist in the Library on iPhone History on iPhone
Subnet Plus on iPad: TLS certificate check Subnet Plus on iPad: traceroute

Works across all your Apple devices

One download, every Apple platform. Subnet Plus is optimized for each screen size, from the folded iPhone Duo to a multi-column layout on iPad, and your saved work follows you everywhere via iCloud.

  • iPhone: iOS
  • iPhone Duo: outer and inner displays, adapts as you fold
  • iPad: full multi-column iPadOS layout
  • Mac: Apple Silicon
  • Apple Vision Pro: visionOS
  • Private iCloud sync across all of them
Subnet Plus app icon

Localization

Available in 45 languages

EnglishSpanish FrenchGerman JapaneseSimplified Chinese Traditional ChineseKorean ArabicPortuguese ItalianDutch RussianPolish TurkishSwedish DanishFinnish NorwegianGreek HebrewCzech SlovakHungarian RomanianCatalan IndonesianMalay ThaiVietnamese UkrainianCroatian SlovenianHindi BengaliTamil TeluguMarathi GujaratiKannada MalayalamPunjabi OdiaUrdu + more

Subnet smarter. Troubleshoot faster.

Free to download. The network toolkit engineers have trusted since 2013.

Download on the App Store