VLSM (Variable Length Subnet Mask)
Calculate VLSM (Variable Length Subnet Mask) instantly with the exact formula and a worked example. Free online calculator — no signup, works on mobile.
VLSM (Variable Length Subnet Mask)
Hosts needed
Required prefix
25
More about: VLSM (Variable Length Subnet Mask)
What it calculates
The “VLSM (Variable Length Subnet Mask)” calculator computes Required prefix from 1 parameter: hosts needed.
Standard IT calculations for developers and sysadmins.
Example calculation
With parameters Hosts needed = 100 the result is 25 (/25).
How to use
- Enter the parameter values — every field above is adjustable with a slider.
- The result and related metrics are calculated automatically as you type.
- Use the additional metrics shown (if any) where needed.
- Copy the result or bookmark the page.