DNS TTL Change Planner

Work out when to lower the TTL and how long the cutover will take.

By TheCalcTools Updated October 17, 2026 Formula checked and tested

Your numbers

Current TTL (seconds)

Temporary low TTL (seconds)

SOA negative-caching TTL (seconds)

Lower the TTL at least this long before cutover

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Worst-case stale time if you do not lower it

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Worst-case stale time after lowering

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Worst-case wait for a brand-new record (negative cache)

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Reduction in cutover window

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Lower the TTL on the record at least one full old-TTL period before the change, so every resolver has fetched the short TTL.

Make the change. Stale answers can last up to the short TTL.

Raise the TTL again afterwards to cut query load.

Lead time ≥ old TTLStale window ≤ TTL in effect when resolvers last cached

Using the default values shown in the calculator:

Current TTL (seconds)	86400
Temporary low TTL (seconds)	300
SOA negative-caching TTL (seconds)	3600

With a 24-hour TTL, lower it at least 24h 0m 0.0s before the switch.
After lowering to 5 minutes, stale answers last at most 0h 5m 0.0s, a 99.7% cut.

Result:

Lower the TTL at least this long before cutover	24h 0m 0.0s
Worst-case stale time if you do not lower it	24h 0m 0.0s
Worst-case stale time after lowering	0h 5m 0.0s
Worst-case wait for a brand-new record (negative cache)	1h 0m 0.0s
Reduction in cutover window	99.7%

Do all resolvers obey TTL?

Most do, but some ISPs and apps enforce minimums or cache longer, so keep the old service running during the window.

What is negative caching?

Resolvers cache an NXDOMAIN answer for the SOA minimum, so a newly created record may be invisible to them for that long.

This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.