How much does headwind affect 5k times.

Did the course start and finish in same location?

No why?

20:59 is 6:45 pace. Entering 6:45 pace and 15 mph headwind, the calculator shows the equivalent pace with no wind would be 5:50 pace. If the headwind was 8mph, the equivalent pace with no wind would be 6:17. Obviously highly dependent on the wind speed.

http://runworks.com/calculator.html

found a calculator for you wrote:

20:59 is 6:45 pace. Entering 6:45 pace and 15 mph headwind, the calculator shows the equivalent pace with no wind would be 5:50 pace. If the headwind was 8mph, the equivalent pace with no wind would be 6:17. Obviously highly dependent on the wind speed.

http://runworks.com/calculator.html

There is no chance that this is accurate.

Wins has a huge impact on me. My heart rates spikes sky high when I run into a headwind. Here's one resource for calculating the impact:

https://lukehumphreyrunning.com/hmmcalculator/race_equivalency_calculator.php

I'm sure there's a more concise explanation available, but here's some of the science behind it if you're a numbers guy and want to calculate it for yourself:

https://blog.stryd.com/2019/12/20/how-does-wind-impact-your-5k-time/

Was this in a workout? A race? It might've felt like 70% but still could have been closer to 50 if you started/finished in the same spot.

I think of wind like hills. You don't make up the time you lose when you're running into it. Are you going to go from 21:00 to 19:00? No. Closer to 20? Sure.

But at 21:00 better & more consistent training can still help you shave off minutes so don't get bogged down in 1 result on a windy day. Keep training & soon enough you'll be well under 20 asking why you were even trying to have this conversation.

Splatter wrote:

found a calculator for you wrote:

20:59 is 6:45 pace. Entering 6:45 pace and 15 mph headwind, the calculator shows the equivalent pace with no wind would be 5:50 pace. If the headwind was 8mph, the equivalent pace with no wind would be 6:17. Obviously highly dependent on the wind speed.

http://runworks.com/calculator.html

There is no chance that this is accurate.

You think it overstates the impact of wind? Who knows what speed wind the OP was talking about when saying "above average". 15 mph is moderately strong. On a bike you can easily go from 20+mph to10mph at the same effort into a strong headwind, so I don't see why 55 sec/mile would be too much. I've been in ~100mph wind before not running - basically crawling and reaching for a wooden railing.

Because you said it was mostly into the wind which I doubt. What direction was the wind from and how far was the finish line from the start? if it was 15MPH west wind and the finish line was 3 miles west of the start line, that is significant. If the wind was 10 MPH and finish line was 1 block to the west of the start line, the wind impact was minimal.

Splatter wrote:

found a calculator for you wrote:

20:59 is 6:45 pace. Entering 6:45 pace and 15 mph headwind, the calculator shows the equivalent pace with no wind would be 5:50 pace. If the headwind was 8mph, the equivalent pace with no wind would be 6:17. Obviously highly dependent on the wind speed.

http://runworks.com/calculator.html

There is no chance that this is accurate.

Putting it another way, 6:45 pace is 8.8 mph, where wind has little impact. 6:45 pace into a 15 mph headwind is 23.8 mph apparent wind, which is tough on a bike due to that wind. And on a bike you'd be able to get into a more aerodynamic position, but when running, you are still straight up and down.

If you push too hard into a headwind, it can wipe you out. Years ago, I ran a 5k at Fort Monroe, Virginia. The guy in front of me would slow down for turns so I passed him at every corner. He'd surge past me on the next straight. From 1.5 to 2.5 miles was along the breakwater with a strong headwind from the bay. I passed him at the corner and sure enough, he surged by me on the breakwater. I let him run into the headwind for the entire mile and passed him when we turned around. I beat him to the finish by more than 30 seconds over the last half mile.

You can't answer the OP's question without knowing how strong the wind is, how tall you are, and how much you slow initially to compensate. However, it's not a zero sum game. If it's an out and back course, you will be slower even though you'll have a tailwind for half the run.

I tried that website. Everything works except the wind function. It tells me to enter a valid pace even though I didn't change anything.

Bower Man wrote:

I tried that website. Everything works except the wind function. It tells me to enter a valid pace even though I didn't change anything.

If you are talking about the runworks website, I was also getting that error message at first from several different entry erros. You have to enter the pace in the lower section. It's not based on the distance and time entered in the top section. Pace has to be entered in the right format: "6:45" vs. "645". And don't forget to click on the radio button on the left side of "Calculate equivalent paces at other windspeeds for the given pace with a ___mph headwind".

At a recent state XC meet w there was a good example of this. 7 of the races have little wind and 3 were run more or less after a 25mph wind story came up. The runners in the 7 low wind races had race times in line with expectations. The other 3 all finished 20-35 seconds slower than expected. I ran the comparisons out of curiosity lining up earlier season results where the kids had been in the same races, and other races on that course.

I've compared my 1km times on an out and back course where I had a headwind in one direction and a tailwind in the other and my times went from 4:20/km to 4:10/km. The wind speed was around 15km/hr (10miles/hr). Converting for all those that still use imperial units that equates to around 1.5 seconds extra per mile/hr of headwind.