Swim To Run Ratio

Updated May 2024

The swim to run ratio in a swimrun event is important for several reasons. But first of all, according to openwaterhq.com, swimming 10km (6.2 miles) is equivalent to running a road marathon, in terms of time taken and energy expended!

This gives you an idea of the energy required during a swim. Approximately, swimming is FOUR TIMES as hard as running, if we compare the 10km swim to the 42.2km marathon.

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Swim To Run Ratio

When it comes to swimrun events, newcomers are sometimes deterred by the swimming involved. This is also true for triathlon, where many triathletes come from a cycling or running background.

Two people in wetsuits swimming in a lake

Image courtesy Gritty Rascals

But the important thing to look at is the swim to run ratio of the event. In general, swimrun races have a swim to run ratio of between 1:8 and 1:4

What does this mean?

If a race has a swim to run ratio of 1:4, it means that for each kilometre you swim, you will run 4 kilometres. It can also be expressed as a percentage, where 1:4 represents 20% swimming and 80% running.

If you are a strong swimmer, you might like to look for events that have a higher swim to run ratio, like 25% (or 1:3). This is relatively high, and not many swimrun races have a ratio that high - but they ARE around!

On the other hand, if you are not a strong swimmer, and are concerned about managing the swim sections, you should look for events that have a low swim to run ratio, like 10% to 12% (or 1:9). This means that only 10% of the total event distance is swimming.

Swim To Run Ratio

A ratio of just 10% swimming is quite low, and there are not a lot of events that have so little swimming compared to running. However, they DO exist! You just have to do some research.

How can you tell what your level your swimming is? It's all very well saying someone is a strong swimmer, but what does that actually mean?

There are 2 aspects to being a strong swimmer;

The pace you can swim at - your speed through the water
How long you can keep it up for - your endurance

As a guide, if you can swim in a pool at 2 minutes per hundred metres, and keep it up for 2,000 metres (2 km), you will be fine in almost any swimrun event up to about 30km. You won't win, but you won't be at the back of the field either!

When I did my first swim run race, I considered myself a reasonable runner (for my age), as I had a 10km time of 47 minutes and a Half marathon time of 1 hour 53 minutes under my belt. I was also a confident swimmer, as I was a competitive swimmer in my youth, but hadn't done much swim training for years.

I anticipated that we would manage OK on the swim legs but make up ground on other teams during the running section. I was wrong. It was the other way around!

We were among the slower runners, often being one of the last teams to reach the first swim entry; but once in the water, we passed teams hand over fist. So, in our part of the field (about half way back), we were relatively slow runners and relatively good swimmers.

The point I'm making here is that you don't have to be a great swimmer to complete (and enjoy) a swimrun event. I have seen people doing the swim legs with breast stroke and even with back stroke!

The trick is to work out how your swimming compares to most other swimrunners, and then pick events with a swim to run ratio that matches your relative ability. At the lower level, I would recommend being able to swim 500 metres in one go in about 20 minutes, at the longest. This sort of ability will ensure that you can manage the swimming in an event with a swim to run ratio of 10% to 12% of the total distance.

We hope this guide is useful; please let us know if you think we have left anything out, using the Contact Us link. Thank you!