Calculate your Eddington Number!

By John Swindells 09 Mar 2023 | Comment
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The Eddington Number is a strangely addictive score for cyclists, devised by British astrophysicist Arthur Eddington for ranking their achievements in an ever-harder scale. Also known as the Eddington Scale, it is defined as "the largest integer E, where you have cycled at least E miles on at least E days (source: triathlete-europe.competitor.com). It not only gives you a nice number that you can show off to your mates, it also comes with clear progression targets for you to achieve ever-higher Eddington numbers. In other words, "how many more days riding of at least x miles do I ride to achieve that score?" Clever, eh?

It doesn't just work for cyclists; runners and swimmers can also apply the scale. The problem is that it's a little bit tricky to calculate your number, as you need to sort all your rides by distance, then bucket them up appropriately. The key to an accurate number is keeping a good record of your activities. An awful lot of people use Strava nowadays, and on that note I've produced a little tool that analyses all of your Strava rides, calculates your Eddington Number, and shows how many more rides you'll need to increase it. So, head over to "My Strava Eddington Number" page, and see what number you get!

For the record, as of March 2023 my number is 126 (it was 110 in September 2020, 90 in October 2017, and 54 in September 2015), and has pretty well stalled there. For the time being I've switched to the metric number (currently 178), with 43 needed to reach the "audax randonneur" magic number of 200. My lifetime target will still be 150 (in miles) so I'm keen to do as many of those as possible in the meantime.

A Summary of Eddington Numbers

Each tab shows the count of Eddington numbers recorded on the My Strava Eddington Number page, so we can get an idea of what are the more common ones.

Switch to the metric (kilometres) version

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9 Comments

by Chris on 29 July 2024
I see a spike in the histogram at 62. Any theories why? I'm guessing that's caused by people aiming for a metric Eddington of 100 x 100km?
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by John Swindells on 29 July 2024
Yes, it's exactly that - people targeting the 100km distance. You can also see a smaller one at E-100.
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by Mike Kear on 08 November 2023
Hi Jon

When a ride is over 24hrs (is it elapsed or riding time? how does E calculate? Eg if I rode 150 miles over 25 hrs what would be added to the E data base? Or say 300 miles over 49 hrs. Thanks Mike

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by John Swindells on 09 November 2023
Hello Mike, I chop up a ride when it starts & finishes in a different day - based on elapsed time. I don't know exactly how far you'll have ridden during each day, so divide it up proportionately by time. Your examples would depend on when they started, but let's assume that it's at midnight. For 150 miles over 25hrs then 144 miles (150*24/25) would be allocated to day 1 and 6 miles to day 2. For 300 miles over 49 hrs, 146.9 miles (300*24/49) would go to each of the first 2 days, and 6.2 miles to the last day.
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by Nick Taylor on 09 July 2023
Veloviewer also calculates this for you.
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by John Swindells on 09 July 2023
Yes, there are a few places that work it out for you 👍
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by David Woodland on 30 March 2022
Hi - this is great fun, really enjoying it. My e number is 81 but 82 has disappeared. For a few weeks the list shows the decreasing number of rides of 83 or more I need for 83 but never a mention of 82! Is it persona non Grata!?
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by John Swindells on 30 March 2022
Glad you're enjoying it, David! As I recall this gap happens if you don't have any 82-mile days to your name, so there's nothing to be gained by riding 82 miles.
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by Emma Swanwick on 10 May 2020
I am looking for the actual maths used to calculate the eddington number, do you have it or know where I can get it?
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by John Swindells on 10 May 2020
Hello Emma, the maths is fairly simple - but it is laborious to keep track of the mileages. You need to maintain a frequency plot of each day's miles ridden - but it also needs to be cumulative. So, if you ride 54 miles in a day, then the 54-mile count increases by 1 - but so does the 53-mile count, the 52-mile count, etc. Your Eddington number is then the greatest mileage which has a count of that mileage.
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by Joe Wein on 02 May 2017
Perhaps if the result falls into the top 10%, you could display it with an extra decimal (assuming you have sufficient data sets for that precision to be meaningful)?
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by John Swindells on 03 May 2017
Interesting suggestion Joe, but I don't think there's enough data at the top end of the stats to justify that level of accuracy.
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by Joris on 16 October 2016
Great site, great tools! What about displaying this graph in a cumulative way, so you van easily see to which best percentage riders you belong, in terms of Eddington numbers.
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by John Swindells on 16 October 2016
Interesting idea, Joris! I could display it as a graph, or maybe I could just tell you what percentile you're in on your personalised Eddington Number page.
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by Vicki on 28 July 2015
Think this is great, thanks...

I take it rides can't be added retrospectively? I used to use Garmin to log rides before strava and tried to add my first few long training rides for comparison, but the E number didn't alter afterwards.

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by John Swindells on 29 July 2015
Hi Vicki, I've just added a link to the E-number page so that you can 'refresh' your score from scratch.

Let me know if that works for you!

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by Tim on 24 March 2015
I'm guessing from your wording that the app uses "rides" rather than "days' mileage", so all my days that I rode to and from work as separate rides will only contribute half each? It makes more sense to do days mileage, otherwise you could log a 200 mile ride as multiple rides and boost your number...
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by John Swindells on 24 March 2015
I've now adjusted my Eddington Number Calculator, so that it's based on distance per day. My score went up by a measly one!
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About the author

My name is John Swindells and I'm a keen recreational cyclist with a preference for long one-day rides. I've also previously dabbled in time trialling and cyclo-cross. See more of what I get up to on Strava!

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