LLM Latency Calculator
🔒 In your browserEstimate response latency from throughput & tokens.
| Time to first token | 500 ms |
| Generation time | 5.56 s |
| Total latency | 6.06 s |
| Effective speed | 90 tok/s |
Estimate = TTFT + (output tokens ÷ throughput). Real latency varies with provider load, prompt size, and streaming.
Disclaimer: Estimates for informational purposes only. Pricing and performance figures come from a community-maintained feed (LiteLLM) with bundled fallbacks and may be outdated or inaccurate. Always confirm current prices on the official OpenAI, Anthropic, Google, or cloud-provider pricing pages before making decisions. ToolsHub is not affiliated with these companies; product names are trademarks of their owners. Token counts for non-OpenAI models are approximate.
About the LLM Latency Calculator
Response time shapes how an AI feature feels. This free LLM latency calculator estimates total response time from the time-to-first-token, the number of output tokens and the model's throughput (tokens per second), so you can design for a target user experience.
It runs entirely in your browser.
How to estimate LLM latency
- Enter the time to first token (TTFT).
- Enter expected output tokens and the model's tokens-per-second throughput.
- See the estimated total response time.
What drives LLM latency
Response time is mostly two things: the time to the first token (the initial delay before anything comes back) plus the output length divided by the model's generation speed in tokens per second. Longer responses and slower models take longer. Streaming tokens as they arrive doesn't change the total but dramatically improves how fast the response feels.
Frequently asked questions
What determines LLM response latency?
Mainly the time to first token (initial delay) plus the output length divided by generation speed (tokens per second). Longer outputs and slower models take longer.
What is time to first token (TTFT)?
The delay between sending a request and receiving the first token of the response — a key driver of how responsive an AI feature feels.
How can I reduce latency?
Shorten outputs, stream tokens as they arrive, use a faster model, and reduce prompt size. Streaming especially improves perceived speed.
How can I reduce perceived latency?
Stream the response so users see text immediately, shorten outputs, trim the prompt, and pick a faster model. Streaming especially improves the experience even when total time is unchanged.
Related searches
Related Calculators tools
🔗 Embed this tool on your website — free
Copy this and paste it into your page's HTML. The tool runs in the visitor's browser, just like here. Change height to fit, or add the optional auto-resize snippet below. Add ?theme=dark to the URL for dark mode.
<iframe src="https://toolhq.dev/embed/llm-latency-calculator/" title="LLM Latency Calculator — ToolsHub" width="100%" height="520" style="border:1px solid #e5e7eb;border-radius:12px;max-width:680px" loading="lazy"></iframe>Optional: auto-resize the iframe height
Add this once on the same page so the iframe grows to fit the tool:
<script>
addEventListener("message", function (e) {
if (e.data && e.data.type === "toolshub:resize") {
document.querySelectorAll('iframe[src*="/embed/"]').forEach(function (f) {
if (f.contentWindow === e.source) f.style.height = e.data.height + "px";
});
}
});
</script>