HTTP request latency model calculator

Calculate simulated completion time and unlimited-slot dependency critical path with your own figures.

Your numbers

Use the units shown. Results update as you change valid inputs.

Use simulated completion time and unlimited-slot dependency critical path to compare changes to your inputs. The method and limits below explain the scope.

Examples

Examples

Try the starting example

Requests: name, dependencies joined by | or none, latency ms, size kB, Mbps
HTML,none,100,10,8 CSS,HTML,20,20,8 JS,HTML,30,40,8 API,JS,100,0,8
Concurrent request slots
2
Simulated completion time (ms)
280
Unlimited-slot dependency critical path (ms)
280
Request start and finish times (ms)
HTML: 0–110; CSS: 110–150; JS: 110–180; API: 180–280
Total request service time (ms)
320

Try another scenario

Requests: name, dependencies joined by | or none, latency ms, size kB, Mbps
HTML,none,100,10,8 CSS,HTML,20,20,8 JS,HTML,30,40,8 API,JS,100,0,8
Concurrent request slots
1
Simulated completion time (ms)
320
Unlimited-slot dependency critical path (ms)
280
Request start and finish times (ms)
HTML: 0–110; CSS: 110–150; JS: 150–220; API: 220–320
Total request service time (ms)
320
Calculation method

Calculation method

Simulated completion time (ms)

Run ready requests in input order when slots are free; each request consumes latency + size kB × 8 / Mbps milliseconds.

Unlimited-slot dependency critical path (ms)

Longest dependency-chain duration with unlimited parallel requests.

Request start and finish times (ms)

Release dependants at parent completion, then use the first available slots.

Total request service time (ms)

Sum all request durations, excluding waiting.

Symbols and units
a
Requests: name, dependencies joined by | or none, latency ms, size kB, Mbps
b
Concurrent request slots

Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.

Assumptions & limits

Assumptions & limits

  • A dependency-aware fixed-duration list schedule with shared concurrency slots. Transfers retain their entered per-request speed even in parallel; DNS, handshakes, multiplexing, parsing and shared bandwidth are not inferred. The limited schedule is not claimed optimal.
Are these inputs private?

These calculations run in your browser. A shared link contains the values you choose to share. Only questions submitted to the separate AI finder are sent to OpenAI.

Further reading

W3C: resource request timing concepts ↗

Background reading; this does not imply endorsement or independent review of SumFizz.

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