DNS

DNS TTL Calculator

Plan DNS record TTL values and understand propagation times. Calculate optimal TTL settings for migrations and changes.

TTL Value

Human readable:

Record Type

Recommended TTL:1 hours

Planning a Change?

Change Checklist

  1. 1Lower TTL to 0s now
  2. 2Wait for old TTL to expire
  3. 3Make your DNS change
  4. 4Restore original TTL after verification

TTL Analysis

TTL Duration
Standard TTL
Min Propagation
typical
Max Propagation
worst case
Seconds Value3,600
Record TypeA
Query Reduction*0%

*Estimated reduction in DNS queries compared to no caching, assuming uniform query distribution.

TTL Quick Reference

60(1 minute)
Failover, load balancing
300(5 minutes)
Dynamic IPs, CDN
900(15 minutes)
Frequent changes
1800(30 minutes)
Moderate changes
3600(1 hour)
Standard records
14400(4 hours)
Stable records
86400(24 hours)
Rarely changed
604800(7 days)
Static records

Best Practices

  • Lower TTL 24-48h before planned changes
  • Use 300-600s for records that may need quick updates
  • Higher TTL (4h+) reduces DNS server load
  • NS and SOA records should have high TTLs (24h+)

Common TTL Values

Seconds Duration Use Case Trade-off
60 1 minute Failover, geo-DNS High DNS load
300 5 minutes CDN, dynamic records Moderate load
3600 1 hour Standard records Balanced
86400 24 hours Stable records Low DNS load
604800 7 days NS, static records Minimal load

Migration Strategy

  • Step 1: Lower TTL 24-48 hours before migration
  • Step 2: Wait for old TTL to expire globally
  • Step 3: Make the DNS change
  • Step 4: Verify, then restore higher TTL

TTL Gotchas

  • Caching layers: Browser, OS, and resolver all cache
  • Minimum TTL: Some resolvers enforce minimums (e.g., 30s)
  • Extended caching: Some ISPs ignore TTL and cache longer
  • Negative TTL: NXDOMAIN responses are also cached