Work out dhcp lease time instantly with clear inputs, formula shown and shareable results.
Lease time trades server load against address recycling speed. If the pool must serve more devices per day than it has addresses, the lease must be shorter than the time each address can be held: roughly 24 hours divided by the number of pool turns. Concurrency follows Little's law — devices per day multiplied by the fraction of a day each one stays.
Lease sizing
turns per day = devices / pool; max hold = 24 / turns; lease = min(max hold, average stay); T1 = 0.5 x lease; concurrent = devices x stay / 24
RFC 2131 sets T1 at 50 percent and T2 at 87.5 percent of the lease, so a client has two chances to renew before the address can be reclaimed.
They multiply DHCP traffic and server writes, and on wireless networks they can cause visible reconnection stalls. Only go below about 15 minutes when the pool genuinely needs fast turnover.