user@netcalc ~/calc $
ipv4_calculator
Calculate network, broadcast, mask, hosts, class and binary for any IPv4 address
ip:
mask:
✓ stdout — ipv4_calculator
Enter runs the calculation · Shift+Enter inserts a new line
user@netcalc ~/calc $
ipv6_calculator
Calculate network info for IPv6 addresses in CIDR notation
ipv6:
pfx:
✓ stdout — ipv6_calculator
user@netcalc ~/calc $
vlsm_calculator
Variable Length Subnet Mask — assigns optimal blocks for each network segment
net:
pfx:
// Subnets required
name:
hosts:
name:
hosts:
name:
hosts:
✓ stdout — vlsm_calculator
| # | Name | Hosts Req | Hosts Avail | Prefix | Network | First Host | Last Host | Broadcast | Mask |
|---|
user@netcalc ~/calc $
usable_ip_range
Shows the exact usable host range for a given network
ip:
mask:
✓ stdout — usable_ip_range
user@netcalc ~/calc $
binary_ip_calc
Convert IP addresses to binary and vice versa, with per-octet visualization
dec:
bin:
✓ stdout — binary_ip_calc
user@netcalc ~/network $
cidr_converter
Convert between CIDR, decimal mask and wildcard. Includes full /1–/32 reference table.
in:
✓ stdout — cidr_converter
📋 CIDR Reference Table
| CIDR | Subnet Mask | Wildcard | Hosts | /24 subnets | Block |
|---|
user@netcalc ~/network $
wildcard_mask_calc
Calculate the wildcard (inverse) mask for Cisco ACLs, OSPF and firewall rules
mask:
✓ stdout — wildcard_mask_calc
user@netcalc ~/network $
supernet_calculator
Find the minimum supernet containing all specified networks (route summarization)
nets:
✓ stdout — supernet_calculator
user@netcalc ~/network $
subnet_splitter
Split a network into equal subnets by specifying a new prefix
net:
mask:
new:
✓ stdout — subnet_splitter
| # | Network | First Host | Last Host | Broadcast | Hosts | Mask |
|---|
user@netcalc ~/network $
range_to_cidr
Convert an IP range (start–end) to the minimum set of CIDR blocks
start:
end:
✓ stdout — range_to_cidr
| # | CIDR Block | Network | Broadcast | Hosts |
|---|
user@netcalc ~/network $
ip_to_integer
Convert IPv4/IPv6 addresses to integer and vice versa
ip:
int:
✓ stdout — ip_to_integer
user@netcalc ~/network $
ipv6_normalize
Expand and compress IPv6 addresses — normalize any valid format
ipv6:
✓ stdout — ipv6_normalize
user@netcalc ~/network $
hex_ip_converter
Convert between hexadecimal and IP address — useful for Windows route tables and Cisco logs
ip:
0x:
✓ stdout — hex_ip_converter
user@netcalc ~/network $
vlan_calculator
802.1Q VLAN info: tag encoding, PCP, DEI, VID, range and compatibility
vlan:
pcp:
dei:
✓ stdout — vlan_calculator
user@netcalc ~/dns $
reverse_dns_generator
Generate the PTR in-addr.arpa zone for an IPv4 network
net:
pfx:
dom:
✓ stdout — reverse_dns_generator
user@netcalc ~/dns $
ipv6_ptr_generator
Generate the PTR ip6.arpa record for an IPv6 address
ipv6:
host:
✓ stdout — ipv6_ptr_generator
user@netcalc ~/dns $
ip_geolocation
Locate a public IP or resolve a domain and geolocate its public address
Domains are resolved through DNS first; geolocation is based on the resulting public IP.
geo:
✓ stdout — ip_geolocation
user@netcalc ~/dns $
ip_address_planner
Interactive IP address space planner — click cells to edit, export to CSV
📋 IP Address Plan
| # | Name | Network | Mask/CIDR | Gateway | VLAN | Location | Notes |
|---|
user@netcalc ~/legal $
Privacy
Data stored in your browser
Theme, language, promotion dismissal and calculation history are stored in localStorage on this device.
Calculations
Calculations are sent through this site's same-origin Worker proxy to the private calculation service.
Performance metrics
LCP, CLS and INP may be stored as aggregate performance measurements by tool and language. Calculation inputs and persistent user identifiers are not included.
GeoIP
Only GeoIP lookups are processed by an external provider. The requested IP address is sent for that lookup.
Issue reports via Telegram
A report link opens the public Telegram bot and includes only the current page slug in the bot start parameter. Calculator inputs and report text are not sent by this website. Text you choose to send inside Telegram is handled by Telegram and the bot.
Cookies and advertising
Advertising is controlled by the production configuration. When Google AdSense is enabled, consent is handled through a certified CMP before personalized advertising is used where required.
Delete local data
Use the button below to clear calculation history. To remove every local preference, clear this site's data in your browser settings.
This page provides operational information; it is not a legal-compliance certification.
VLSM step by step with a real subnet plan
Learn a repeatable VLSM method: sort requirements, choose prefixes, allocate networks and verify the final plan.
01
Sort requirements from largest to smallest
VLSM is easiest when host requirements are ordered first. Allocate the largest subnet before smaller ones so large blocks remain aligned and you do not strand unusable address fragments between assignments.
02
Convert each requirement to a prefix
For each segment choose the smallest prefix that satisfies the required capacity plus realistic growth. A requirement around 100 classic hosts points to /25, around 50 to /26 and around 25 to /27. Point-to-point links may have different rules.
03
Allocate sequentially on valid boundaries
Start at the parent network boundary and place each child network on a boundary valid for its prefix. After every allocation, advance to the next address after the block before placing the next subnet.
04
Verify before implementation
Check that no child networks overlap, all remain inside the parent and reserved growth space is deliberate. Document VLAN, gateway, purpose and location with the subnet so the plan remains useful after deployment.
05
Reserve growth without destroying summarization
Growth space is most useful when it is intentional. Keep future blocks adjacent to the site or function they belong to, rather than sprinkling small unused ranges everywhere. That makes later expansion easier and preserves the possibility of advertising a clean aggregate upstream.
06
Think about route summaries while allocating
A technically valid VLSM plan can still produce an ugly routing table. If several VLANs belong to the same site, align them inside a larger summarizable boundary where possible. This lets an access or distribution layer advertise one aggregate instead of many unrelated specifics.
07
Treat the address plan as configuration data
A subnet plan should include owner, VLAN, gateway convention, DHCP/static split, location and status. Exporting the result into IPAM or a documented source of truth is what turns a one-time calculation into an operational design.
EX
Worked example
- Assume 10.20.0.0/24 must host segments for 100, 50, 20 and 10 devices.
- Sort them as 100 → 50 → 20 → 10 and map them to /25, /26, /27 and /28.
- Allocate 10.20.0.0/25, 10.20.0.128/26, 10.20.0.192/27 and 10.20.0.224/28 on valid boundaries.
- Keep the remaining addresses documented as reserve instead of silently consuming them later.
✓
Operational checklist
- Sort requirements before assigning anything.
- Verify every child is inside the parent and does not overlap.
- Leave deliberate reserve space for growth.
- Document VLAN, gateway and summary boundary with each prefix.
Tools to apply it
Standards and references
🕐 History