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Disclaimer

Last updated: October 2026

The tool this page covers is PacVivo, a running pace and race-time calculator. Put simply, it converts between pace, distance and finish time and predicts marathon, half-marathon, 10K and 5K times from a recent race, and the way it does so is this: it predicts using the Riegel formula, where the predicted time scales as the ratio of the distances raised to the power 1.06, which is why an equivalent performance at twice the distance is a little slower than twice the time. Everything stated here applies to that tool and the values it handles, and to nothing else.

In day-to-day use the tool works only from your recent race time and distance, and it is usually opened for things like setting a target pace for a marathon. None of that reaches us, so none of it can be stored.

General information only

Nothing on pacvivo.com is professional advice. What PacVivo produces is an estimate of a calculation rather than a measured fact, published for general information and education.

General-purpose tools

The tools here return a fast, general answer. Where a PacVivo result carries a consequence — something that gets built from, filed, or paid — check it independently first.

Links to third-party sites

Any link to another site is provided for convenience. That content is outside our control and we are not answerable for it.

Advertising

The Site is funded by advertising. No advertiser has any say over a result, and no ad should be read as an endorsement.

No warranty of any kind

The assumption that matters most for PacVivo is that your input matches the model. It predicts using the Riegel formula, where the predicted time scales as the ratio of the distances raised to the power 1.06, which is why an equivalent performance at twice the distance is a little slower than twice the time. When it does not — or when rounding, unit handling or browser behavior intervenes — no warranty attaches to the Site, careful as we are with the method.

Before you act on a result

Before you act on any figure from this site, confirm it fits your circumstances. If you spot something wrong, use the contact page — we would rather correct it than defend it.