How is reaction time measured?

A trial starts when the ready callback records its timestamp and ends when the page's event handler records your click or key response. The randomized wait is scheduling time and is not included in a completed trial, and early responses are discarded.

What statistics are reported?

Valid trials report best, arithmetic mean, median, and spread across all accepted trials. The retained set is limited to 100 completed trials, and the five-row Recent Results section is only a view of the newest five.

Is this a measure of neurological reaction time?

No. It measures browser-observed latency from the callback that starts the prompt until your event reaches the page. Display rendering, the event loop, the operating system, and the input device can add delay, and the browser can coarsen timer resolution.

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Choose the tool whose inputs and output match your task. Check each calculator’s assumptions and limitations before using its result.

Latest update: Aug 14, 2026

Strength-training tools turn one measured effort into a planning number. The reaction time calculator times how quickly you respond to a signal, which athletes use to track focus and drills. For translating a completed set into an estimated maximum, the one rep max calculator applies the Epley, Brzycki, and Lombardi equations to the weight and repetitions you enter. Choose the tool that matches the quality you measured: a response time for reaction drills, or a lifted weight with its repetitions for max-strength planning. Find more measured-performance tools in the Sports & Performance collection.

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Reaction Time Calculator

Measure browser-observed latency for a visual prompt and summarize repeated trials.

Updated Aug 14, 2026

Verified Aug 14, 2026

Frequently asked questions

How is reaction time measured?: A trial starts when the ready callback records its timestamp and ends when the page's event handler records your click or key response. The randomized wait is scheduling time and is not included in a completed trial, and early responses are discarded.
What statistics are reported?: Valid trials report best, arithmetic mean, median, and spread across all accepted trials. The retained set is limited to 100 completed trials, and the five-row Recent Results section is only a view of the newest five.
Is this a measure of neurological reaction time?: No. It measures browser-observed latency from the callback that starts the prompt until your event reaches the page. Display rendering, the event loop, the operating system, and the input device can add delay, and the browser can coarsen timer resolution.