VLSM规划
在浏览器中计算。无需注册，不上传IP。
Primary controls: 简体中文. Detailed guidance and some secondary labels are in English.
IPv4计算
在浏览器中计算。无需注册，不上传IP。
See the boundary, bit by bit.
Blue bits identify the network. Gray bits identify the host. Change the prefix to see the boundary move.
IPv6计算
VLSM规划
Enter each LAN’s required hosts. Largest blocks are allocated first. LAN mode reserves network and broadcast addresses.
CIDR工具
Merge overlapping and adjacent blocks without adding addresses. IPv4 and IPv6 are supported separately. Maximum 512 entries.
Range → CIDR
Check containment
子网划分
32 results per page. CSV exports the displayed page only; the full subnet count is calculated exactly.
练习
Find the mask first. Network = address AND mask. The block contains 2^(32 − prefix) addresses.
Your score stays in this tab. Revealed answers count as missed; repeat checks never increase the score.
Calculate with confidence.
Start with an IP address or mask. See the network boundary, address range and exact counts together.
Build a plan that fits.
Allocate VLSM blocks, spot overlapping ranges and combine CIDRs without expanding the address space.
Understand the result.
Explore binary boundaries, read concise guides and practice with step-by-step solutions. Export when you are ready.
IPv4 at a glance.
Prefix, mask, and capacity.
| CIDR | 子网掩码 | 地址总数 | 可用地址 |
|---|---|---|---|
| /0 | 0.0.0.0 | 4,294,967,296 | 4,294,967,294 |
| /1 | 128.0.0.0 | 2,147,483,648 | 2,147,483,646 |
| /2 | 192.0.0.0 | 1,073,741,824 | 1,073,741,822 |
| /3 | 224.0.0.0 | 536,870,912 | 536,870,910 |
| /4 | 240.0.0.0 | 268,435,456 | 268,435,454 |
| /5 | 248.0.0.0 | 134,217,728 | 134,217,726 |
| /6 | 252.0.0.0 | 67,108,864 | 67,108,862 |
| /7 | 254.0.0.0 | 33,554,432 | 33,554,430 |
| /8 | 255.0.0.0 | 16,777,216 | 16,777,214 |
| /9 | 255.128.0.0 | 8,388,608 | 8,388,606 |
| /10 | 255.192.0.0 | 4,194,304 | 4,194,302 |
| /11 | 255.224.0.0 | 2,097,152 | 2,097,150 |
| /12 | 255.240.0.0 | 1,048,576 | 1,048,574 |
| /13 | 255.248.0.0 | 524,288 | 524,286 |
| /14 | 255.252.0.0 | 262,144 | 262,142 |
| /15 | 255.254.0.0 | 131,072 | 131,070 |
| /16 | 255.255.0.0 | 65,536 | 65,534 |
| /17 | 255.255.128.0 | 32,768 | 32,766 |
| /18 | 255.255.192.0 | 16,384 | 16,382 |
| /19 | 255.255.224.0 | 8,192 | 8,190 |
| /20 | 255.255.240.0 | 4,096 | 4,094 |
| /21 | 255.255.248.0 | 2,048 | 2,046 |
| /22 | 255.255.252.0 | 1,024 | 1,022 |
| /23 | 255.255.254.0 | 512 | 510 |
| /24 | 255.255.255.0 | 256 | 254 |
| /25 | 255.255.255.128 | 128 | 126 |
| /26 | 255.255.255.192 | 64 | 62 |
| /27 | 255.255.255.224 | 32 | 30 |
| /28 | 255.255.255.240 | 16 | 14 |
| /29 | 255.255.255.248 | 8 | 6 |
| /30 | 255.255.255.252 | 4 | 2 |
| /31 * | 255.255.255.254 | 2 | 2 |
| /32 * | 255.255.255.255 | 1 | 1 |
/31 assumes a point-to-point link. /32 is a single address. Counts do not exclude special-purpose address ranges.
Questions, answered.
Are my IP addresses sent to a server?
The calculators run entirely inside your browser. Entered addresses and network names are not uploaded or saved by SubnetTidy. Advertising and optional analytics make separate requests; they do not receive calculation inputs through our code.
How are /31, /32 and IPv6 handled?
IPv4 /31 uses the two-endpoint point-to-point interpretation in RFC 3021. A /32 is one address. IPv6 uses exact 128-bit arithmetic and does not subtract an IPv4-style network/broadcast pair.
Can I export my work?
Use Copy or Export for local text, JSON and CSV results. Nothing is automatically saved. VLSM exports the full plan; subnet splitting exports only the current page. Close the tab only after exporting results you need.
Does the tool check live network connectivity?
No. It performs address arithmetic and planning. It does not scan hosts, check routing, change devices or verify whether an IP is publicly reachable. Validate real deployments against your own network and provider rules.