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Write a network in CIDR notation and get the mask, the range of usable addresses, the broadcast and how many hosts fit inside.
Example: 192.168.1.0/24, 10.0.0.0/8 or 192.168.1.10 255.255.255.0. Nothing leaves your browser.
It is how many bits of the address identify the network. The remaining bits are for the hosts: /24 leaves 8 bits, that is 256 addresses, 254 of them usable.
The first one names the network itself and the last one is the broadcast address. In a /31 and a /32 that rule does not apply: they are used for point-to-point links and for single hosts.
Yes. 255.255.255.0 and /24 are the same thing written two ways. The calculator shows both so you can copy whichever your panel asks for.
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