TTL in DNS — What It Is and How to Calculate [2026]

Enterno.io Editorial Team

TTL: Definition and Use Cases

By Anatoly Oshmanovsky · Updated Apr 17, 2026

TL;DR:

TTL (Time to Live) in DNS is the number of seconds resolvers cache a DNS record before querying again. Typical values: 300 (5 min — for frequently changing records), 3600 (1 hour — standard), 86400 (24 hours — stable records). Low TTL = fast change propagation but more queries.

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What is TTL

Check TTL online

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TTL in sec/min/hrTTL conversion and calculation

Propagation TimeWhen DNS changes will take effect

DNS CacheHow long records are cached

RecommendationsOptimal TTL values for different scenarios

Why teams trust us

TTL

instant conversion

48h

max propagation time

300

TTL for migration

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How it works

Enter TTL in seconds

Convert to h/min/days

Calculate propagation window

What is TTL and why does it matter?

TTL (Time To Live) in DNS defines how long resolvers cache a record. Choosing the right TTL affects how fast DNS changes propagate and the load on the authoritative server.

TTL Calculator

Convert seconds to readable format and back: 86400 = 1 day.

Propagation Window

Estimate when a DNS record change will be visible to all users worldwide.

Migration Scenarios

TTL recommendations before server migration: when to lower, when to restore.

Common Values

Reference for standard TTLs: 300, 3600, 86400 — which to use for which records.

Who uses this

DevOps

DNS migration planning

Sysadmins

TTL record optimization

DNS admins

cache time calculation

Developers

TTL understanding for APIs

Common Mistakes

❌

Migration with high TTLWith 86400s TTL, some users will see the old IP for a day after the change.

❌

TTL = 0 alwaysZero TTL increases NS server load and slows resolution for users.

❌

Not pre-lowering TTLTTL reduction only takes effect after the current TTL expires. Lower 24–48 hours before migration.

❌

Same TTL for everythingMX and NS are better with high TTL (86400), A records with moderate (3600).

Best Practices

✓

Lower TTL to 300 48 hours before migrationThis ensures fast switching after the IP change.

✓

Use 3600 for A recordsOne hour is a balance between propagation speed and server load.

✓

86400 for stable NS/MXName servers change rarely — high TTL reduces load.

✓

Restore TTL after migrationReturn to standard TTL after successful migration.

Monitor DNS records automatically

DNS monitor notifies you when A, MX, or TXT records change.

Learn more

Glossary

TTL: Definition and Use Cases

Frequently Asked Questions

Do I need TTL?

If you work with web infrastructure or APIs, almost certainly yes. See the article above for specific use cases.