Tech & Engineering

IP & Domain Tools Calculators

Subnets, CIDR, IPv6, MTU, DNS and domain calculators. Free calculators with formulas and worked examples.

Subnetting

IPv4 Subnet CalculatorEnter an IPv4 address and prefix length to get the network, broadcast, mask and host range.CIDR Prefix to Hosts CalculatorPick a prefix length and see the address count, usable hosts and mask.Subnet Mask to CIDR Prefix CalculatorEnter a subnet mask to get the CIDR prefix, wildcard mask and usable hosts.Hosts to Subnet Prefix (VLSM) CalculatorEnter hosts needed and growth to get the right subnet size.Subnet Split Calculator (Equal Subnets)Divide a parent network into the number of equal subnets you need.

IP addressing

IP Address to Binary, Hex and Decimal ConverterConvert any IPv4 address into binary, hex and decimal.Is This IP in the Subnet? CheckerTest an IP against a CIDR block.IP Pool Exhaustion CalculatorSee how many months of addresses your pool has left.

Routing

Route Summarization CalculatorFind the supernet that covers a run of contiguous subnets.

IPv6

IPv6 Subnet CalculatorEnter the allocated prefix and the subnet size to get counts.

Network performance

MTU and TCP MSS Calculator (GRE, VXLAN, GTP, IPsec)Find the safe inner MTU and MSS for your tunnel.Packets per Second to Bits per Second CalculatorConvert between pps and bandwidth for any packet size.Ethernet Frame Efficiency and Goodput CalculatorSee how much of a link's speed carries real data.Serialization and Propagation Delay CalculatorBreak latency into serialization and propagation parts.Ping RTT to Distance CalculatorTurn a ping time into a maximum possible distance.

Mobile and ISP

CGNAT Public IP Pool Sizing CalculatorSize your CGNAT public pool from subscribers and ports.

Domain and DNS

DNS TTL Change PlannerWork out when to lower the TTL and how long the cutover will take.

About these calculators

Practical calculators for network engineers, sysadmins and website owners: CIDR and netmask conversion, subnet checks, VLSM, IPv6 planning, packet and link maths, DNS timing and domain costs. Results are theoretical; always confirm on your own equipment.

Each calculator explains its formula, includes a worked example and lists its sources. Read how we check them on our editorial policy page, or browse all calculators.

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Please note: TheCalcTools gives general estimates for information and education. It is not financial, medical, legal or tax advice, and results should be checked before you make a decision. See our disclaimer and about page.