DHCP Range Calculator

Type an address, CIDR, and reserve. 192.168.1.0 and /24 give 192.168.1.1. 10.0.0.0/24 and 10 give 10.0.0.11. 172.16.0.0 /16 and 1 give 172.16.0.2. Address math, not a router.

This is an IPv4 pool after network and reserve, not a lease table from a router. The mask sits on the IP subnet calculator.

Input data

You can enter any host in the subnet plus CIDR. “Reserved” skips the first usable addresses (e.g. gateway / static).

Results

Enter data and click Calculate.

How it works

DHCP Range Calculator in this calculator computes the pool start from CIDR. 192.168.1.0 and /24 give 192.168.1.1. 10.0.0.0/24 and reserve 10 give 10.0.0.11. 172.16.0.0, /16 and reserve 1 give 172.16.0.2. The calculator does not read a router and does not read leases.

Field dhcp-addr is an address or IP/CIDR. Field dhcp-cidr is the prefix. Field dhcp-reserve skips the first N usable hosts. /24 with no reserve starts at .1. Reserve 10 on 10.0.0.0/24 starts at .11. Reserve 1 on /16 starts at .2.

192.168.1.1 is not a MikroTik row. 10.0.0.11 does not come from dnsmasq. 172.16.0.2 is not ISC dhcpd. You type the three fields. This is address math.

The IP subnet calculator counts hosts. The DNS TTL calculator computes the wait before a record change. Here 192.168.1.0 /24 stays 192.168.1.1, the pool start alone.

Type 192.168.1.0, CIDR 24, and reserve 0, then Calculate. The result is 192.168.1.1. 10.0.0.0/24 also works in the address field. A blank IP gives no start.

192.168.1.0 /24 gives 192.168.1.1. 10.0.0.0/24 and 10 give 10.0.0.11. 172.16.0.0 /16 and 1 give 172.16.0.2. Another reserve at /24 changes the start.

Formula

start = first usable + reserve. Network and broadcast stay outside the pool. IPv4 math, not a router.

How to use

  1. Type 192.168.1.0, CIDR 24, and reserve 0.
  2. Click Calculate. The pool start is 192.168.1.1.
  3. 10.0.0.0/24 and 10 give 10.0.0.11. 172.16.0.0 /16 and 1 give 172.16.0.2.
  4. Address math, not a router.
  5. The next card counts a CIDR mask and hosts.

192.168.1.0 /24 gives 192.168.1.1

Start = first usable + reserve. 192.168.1.0 /24 gives 192.168.1.1. Not a router.

DHCP
A pool sketch, not a lease. 192.168.1.0 /24 leaves 192.168.1.1.
Range
The pool start. 10.0.0.0/24 and 10 give 10.0.0.11.
Calculator
IPv4 math. 172.16.0.0 /16 and 1 give 172.16.0.2.

Examples

Example 1

  • 192.168.1.0
  • CIDR 24
  • reserve 0

192.168.1.1

What DHCP start at 192.168.1.0 /24? 192.168.1.1. Address math, not a router.

Example 2

  • 10.0.0.0/24
  • CIDR 24
  • reserve 10

10.0.0.11

What start at 10.0.0.0/24 and reserve 10? 10.0.0.11.

Example 3

  • 172.16.0.0
  • CIDR 16
  • reserve 1

172.16.0.2

What start at 172.16.0.0 /16 and reserve 1? 172.16.0.2.

Related calculators

IP Subnet / CIDR

IP Subnet / CIDR Calculator: an IPv4 address and a CIDR prefix.

Use calculator →

DNS TTL Calculator

DNS TTL: 86400 and 300 mean a 24 h wait before the record change.

Use calculator →

IPv6 shorthand

IPv6 Shorthand Calculator: RFC 5952: strip leading zeros, one :: on the longest zero run.

Use calculator →

MTU and IP fragmentation

MTU and IP Fragmentation: packet, MTU, and header.

Use calculator →

All IT calculators

Common questions

What start at 192.168.1.0 /24 and reserve 0?

192.168.1.1. The first usable. Not a router.

What about 10.0.0.0/24 and reserve 10?

10.0.0.11. Ten hosts skipped after .1.

What about 172.16.0.0 /16 and reserve 1?

172.16.0.2. One host reserved after the network.

Is this a lease table from a router?

No. The calculator does not talk DHCP. Three fields only.

Is 10.0.0.0/24 in the address enough?

Yes. The prefix can live in the address. The example CIDR stays 24.

Do network and broadcast enter the pool?

No. Start is after the network address and after the reserve.

How is this different from IP subnet?

That card counts hosts. Here 192.168.1.0 /24 gives 192.168.1.1.

Does a blank IP count?

No. Without an address there is no pool start.

Is this a .100-.199 home-router pool?

No. The model is a tail after reserve, not a mid-block GUI range.

Knowledge sources

The calculator counts bits, bytes or throughput from your numbers. Below are SI and bit definitions (NIST).

Page updated in 2026.

What a DHCP range is

A DHCP range (pool) is a contiguous block of IPv4 addresses that a DHCP server leases to clients — laptops, phones, printers, IoT. On a router or DHCP server you typically set a start and end address (or start + count). This calculator derives start and end from the subnet (IP/CIDR) plus an optional reservation of the first usable hosts.

The pool is not the whole subnet. Network and broadcast (on a classic LAN) must not be leased. Gateway, DNS servers, domain controllers, and network printers usually stay outside the pool — either as MAC reservations or as exclusions before the pool start.

DHCP range vs usable host range

  • Usable host range — on a classic LAN, every address between network and broadcast (e.g. 192.168.1.0/24: .1–.254, 254 hosts).
  • DHCP range — a subset of usable hosts the server may assign. Often narrower: keep the low end for gateway/static, use the middle or high end for DHCP.
  • Reservation in this calculator — skips the first N usable addresses from the network side. Reservation 1 on a /24 usually means: gateway .1 outside the pool, pool from .2.
  • MAC reservations — a separate server feature: a client always gets the same IP (often still inside the pool). Do not confuse with the form’s “reserved hosts”.

Example: usable 192.168.10.1–254, but DHCP pool .100–.199 (100 addresses). .1–.99 and .200–.254 stay for static / future use. This tool models “pool from first usable after reservation through the last usable.” For a mid-block pool (.100–.199), confirm the CIDR here, then set start/end manually on the router using the home example below.

How to choose start and end

  • Count devices — concurrent DHCP clients plus 20–50% headroom for guests, phones, and new IoT.
  • Protect infrastructure — typically keep .1 (or the first few) out of the pool; servers often live in .2–.20 or another VLAN.
  • Avoid neighbor VLAN overlap — start and end must sit inside the same CIDR. Cross-check with the subnet calculator.
  • Lease time vs pool size — short leases (1–4 h on guest Wi‑Fi) stretch a smaller pool; long home leases (1–7 days) need enough addresses for stable devices.
  • Document it — record CIDR, gateway, DHCP pool, and static range in VLAN notes — speeds up IP-conflict troubleshooting.

Quick DHCP pool planning table

Example layouts: usable hosts vs a safer mid-range pool vs addresses kept outside DHCP.

SubnetUsable hostsExample DHCP poolOutside the pool (idea)
192.168.1.0/24.1–.254 (254).100–.199 (100).1–.99 gateway/static; .200–.254 spare
10.20.30.0/24.1–.254 (254).50–.200 (151).1–.49 gateway + servers/printers
10.0.5.0/26.1–.62 (62).10–.50 (41).1–.9 infrastructure; remainder spare

The “reserved hosts” field builds a pool from the first usable after N through the end of the block — not a mid-range (.100–.199). Enter mid-range start/end manually in the router.

Home /24 example (.100–.199)

Network: 192.168.1.0/24. Usable hosts: .1–.254.

  • Gateway / router: 192.168.1.1 (outside DHCP).
  • Static (optional): .2–.20 — NAS, printer, Pi, cameras.
  • Typical DHCP pool: 192.168.1.100–192.168.1.199 → 100 addresses for laptops, phones, TVs, guests.
  • Headroom: .200–.254 for future static or a second pool.

In this calculator, 192.168.1.0/24 with reservation 1 yields .2–.254 (wide pool). If your router only accepts start/end, enter .100 and .199 from the plan above — the CIDR and usable-host counts still verify that the plan fits in /24.

Quick check: enter 192.168.1.50/24, reservation 1 — network should be 192.168.1.0/24, pool start .2.

Small office / VLAN example

Staff VLAN: 10.20.30.0/24. L3 gateway: 10.20.30.1. Printers/scanners: .5–.15 (static). DHCP on the controller/firewall.

  • Calculator reservation = 15 → pool 10.20.30.16–10.20.30.254 (239 addresses) when static occupies the low end.
  • Or a tighter pool: .50–.200 (151 addresses) with slack on both ends.
  • Separate guest VLAN (10.20.40.0/24) with its own DHCP pool and isolation — do not mix guests into the staff subnet.
  • In a VPC the same idea applies: subnet CIDR + cloud DHCP options; plan how many IPs are for ENIs vs ephemeral clients.

/26 office slice: 10.0.5.0/26 → 64 addresses, 62 usable. Reservation 2 (gateway + jump host) leaves 60 pool addresses — fine for a small branch, tight if you add many IP scanners.

When the subnet is too small (/30, /31, /32)

  • /30 — 4 addresses, 2 usable. Typical point-to-point link. DHCP almost never makes sense; both IPs are usually static.
  • /31 (RFC 3021) — 2 addresses, both usable on P2P. No classic network/broadcast pair. DHCP here is atypical; the result shows a special note.
  • /32 — single host / host route. No DHCP pool.
  • /29–/28 — small DMZ or lab (6–14 usable). DHCP is possible, but reservation 1–2 eats the pool quickly — count carefully.

If the calculator warns or returns an empty pool, do not force DHCP — enlarge the subnet (e.g. /30 → /29) or use static addressing.