Running pace expresses the time you need to cover one kilometre or mile, while speed shows how far you travel within an hour. Tracking both metrics helps you judge aerobic capacity, compare sessions consistently, and adjust workout intensity across training phases. Understanding the relationship between the two enables smarter goal setting for events from 5K races to marathons.

This calculator lets you enter any two of distance, time, pace, or speed and instantly derives the remaining values. For example, type 10 km and a target pace of 5:00 min/km to see the required 50-minute finish time plus kilometre-by-kilometre splits that keep you on schedule. The interface updates live, so tweaks reveal how small adjustments influence overall performance.

Open the tool before long-run planning, race strategy reviews, or coaching discussions to translate goals into actionable splits and expected finish times. You can bookmark specific scenarios to revisit progress each week. Consult a healthcare professional before starting intensive training or if you experience discomfort; the information here supports, but does not replace, qualified advice.

Technical Details:

All logic executes client-side in plain JavaScript, combining responsive form controls with Bootstrap utilities. Values recalculate on every keystroke using unit-aware arithmetic, while an optional query-string encoder preserves state for shareable links. Because no requests leave your browser, data privacy is absolute, even when offline.

Automatic unit conversion

Entering kilometres or miles instantly synchronises every dependent field, preventing mismatched units and removing manual arithmetic.

Live split table

Each edit redraws a kilometre- or mile-by-mile table so you see target cumulative times; for instance, a 5:00 pace shows 25:00 at the halfway mark.

Two-way control binding

Changing pace recalculates finish time; updating time recalculates pace, ensuring consistent outputs whatever you choose to edit.

Sharable session URLs

The current scenario compresses into the address bar, letting you bookmark workouts or email plans to friends without exporting files.

Accessibility enhancements

Form controls support keyboard increments, ARIA labels, and clear focus styling, improving use for screen readers and power users alike.

Calculations & Scoring:

The tool applies straightforward relationships between distance (d), time (t), pace (p), and speed (s):

p = t ÷ d            # min : sec per unit
s = d ÷ (t / 3600)   # km/h or mph
t = d × p            # hh:mm:ss

To populate the split table, it adds p successively until the chosen distance is reached. Data Privacy: all calculations run locally within your browser environment; no information is transmitted.

Step-by-Step Guide:

Follow these steps to convert metrics and generate splits.

Enter a value in Distance and select Kilometres (km) or Miles (mi).
Fill in Time using the hh, mm, and ss fields .
Optionally open Advanced, set a Target Pace or Speed, then click Apply.
Switch to the Splits tab to view per-unit times and adjust strategy if needed.

FAQ:

Answers to frequent questions.

Is my data stored?

No. The application never sends or saves personal input; closing the tab clears everything unless bookmarked.

Can I use custom race distances?

Yes. Enter any positive number such as 21.1 for a half-marathon or 42.195 for a full marathon.

How accurate are the results?

They rely on exact unit conversions and your provided values; environmental factors like terrain can still affect real-world pacing.

What browsers are supported?

Any modern browser with ES6 support works offline and online, including desktop and mobile versions.

Do split times update automatically?

Yes. They refresh after every edit, ensuring you always view current projections.

Troubleshooting:

Resolve common issues quickly.

Blank results: Ensure distance and time are both positive numbers.
Incorrect unit conversion: Re-select your unit from the dropdown to force recalculation.
Decimals rounded unexpectedly: Use the stepper arrows or type extra decimal places as needed.
Split table not visible: Check the Splits tab is active and distance is at least one full unit.
Share link not copying: Right-click the address bar and choose Copy if the dedicated button fails.

Advanced Tips:

Gain extra value from the calculator.

Model negative splits by reducing target pace halfway through and observing updated tables.
Create interval workouts by bookmarking separate fast and recovery configurations.
Use miles for international race plans, then switch to kilometres to match local training routes.
Compare bike speed against run pace by toggling to high velocities.
Embed the tool in a training blog with an <iframe> to share interactive plans.

Glossary:

Key terms used throughout the tool.

Pace: Time required to cover one kilometre or mile.
Speed: Distance travelled per hour, expressed in km/h or mph.
Split: Intermediate time marker at regular distance intervals.
Negative split: Running the second half of an event faster than the first.
PB: Personal best record for a given distance.

Metric	Value
Total time	{{ timeReadable }}
Pace	{{ paceReadable }}
Speed	{{ speedReadable }}

Pace & Speed Calculator