DNS Latency Input Form
Enter measured lookup samples and environment values to estimate effective DNS performance.
Example Data Table
Example scenarios show how different resolver responses affect averages, jitter, tail latency, and scoring.
| Resolver | Record Type | Sample Latencies (ms) | Average (ms) | Jitter (ms) | P95 (ms) | Score |
|---|---|---|---|---|---|---|
| Resolver A | A | 14, 18, 16, 15, 17 | 16.00 | 1.41 | 18.00 | 91 |
| Resolver B | AAAA | 22, 28, 25, 27, 24 | 25.20 | 2.14 | 28.00 | 78 |
| Resolver C | MX | 35, 42, 37, 39, 44 | 39.40 | 3.26 | 44.00 | 64 |
Formula Used
1) Average Raw Lookup
Average = Sum of sample latencies / Number of samples
2) Jitter
Jitter = Standard deviation of sample latencies
3) Uncached DNS Latency
Uncached Latency = Average + Network RTT + Transport Overhead + DNSSEC Overhead + Queue Delay
4) Cache-Adjusted Latency
Cache Factor = 1 - (0.75 × Cache Hit Rate)
Cache-Adjusted Latency = Uncached Latency × Cache Factor
5) Effective DNS Latency
Effective Latency = Cache-Adjusted Latency × (1 + Packet Loss % + Retry Count × 0.08)
6) Estimated Page DNS Delay
Page DNS Delay = Effective Latency × Page DNS Requests
7) DNS Efficiency Score
Score = 100 - Latency Penalty - Jitter Penalty - Loss Penalty - Retry Penalty - Timeout Penalty
How to Use This Calculator
- Enter the domain or hostname you want to evaluate.
- Select the record type being queried, such as A or AAAA.
- Paste several measured DNS lookup times in milliseconds, separated by commas.
- Add environment values like RTT, transport overhead, DNSSEC delay, and resolver queue delay.
- Enter cache hit rate, packet loss, retry count, page DNS requests, and target latency.
- Click Calculate DNS Latency to show the result above the form.
- Review the score, sample table, and Plotly graph for performance trends.
- Export the output using the CSV or PDF buttons.
Frequently Asked Questions
What is DNS latency?
DNS latency is the time needed to resolve a hostname into records such as A or AAAA. Lower latency helps browsers, apps, APIs, and services begin connections faster.
Why should I enter multiple samples?
Single readings can hide spikes or cached replies. Multiple samples reveal average delay, jitter, and high-percentile behavior, which better reflect real troubleshooting conditions.
How does cache hit rate affect the result?
Cached responses usually return faster than uncached lookups. A higher cache hit rate lowers estimated effective latency because fewer requests require full recursive resolution.
What does jitter mean here?
Jitter is the standard deviation of your sample timings. Higher jitter suggests inconsistent resolver performance, congestion, routing variation, or intermittent packet loss.
What is P95 latency?
P95 latency is the value that 95 percent of samples stay below. It highlights tail delays and is useful for spotting spikes that averages can hide.
Why include packet loss and retries?
Packet loss and retries stretch lookup completion time because failed or delayed responses often trigger retransmissions. Including them makes the estimate closer to real network conditions.
Can this replace live network testing?
No. This calculator estimates and compares performance from the values you provide. Use it alongside dig, drill, nslookup, packet captures, and monitoring for direct measurement.
What score is considered good?
A score above 85 usually indicates efficient and stable resolution relative to your target. Scores between 70 and 84 are workable, while lower values deserve investigation.