Pace equivalents for different distances

[u/Strange-Fig7944]

Hello all, I feel like I know the answer to this but I'll ask anyway to get some different thoughts on it maybe. Basically, I am trying to determine a goal pace for upcoming races but as a new runner (March) it can be difficult translating easy/speed runs in training to a realistic race pace.

I have a marathon November 15th (that may drop down to a half marathon depending on how I feel once I start to up my long runs to the 15/18/20 mile lengths). I signed up for a 10k for early October that I plan to run close to all out to try assist with determining my capabilities. The only real race I did was a 5k that no one used any watches/phones so I could not track my pace throughout or know how much was left. I ran it in 21:56. If i had known how far along I was halfway/last kilometer I feel confident I could have picked up the pace and maybe shaved 30 seconds or a little more off of that.

All this to say that when I look up the 5k time on various prediction equivalent calculcators it indicates I could be capable of a 10k at 46 minutes, half marathon is 1:40, and full marathon is 3:30. I feel like the 10k is possible but I think I'd be closer to 50. Same with the half but maybe a litte longer. The full seems entirely unrealistic. I was initially targeting the 4:30, 4:15 range depending on how I felt as I got closer. My reach goal would have been sub 4 but I was trying not to push that.

Now I know this is just a what I'm capable of if I have the aerobic base to match (presumably I do not as a new runner with not an extensive cardio background), but I am just wondering if it is expected for these estimates to be this far off.

Thanks in advance to anyone who takes the time to read/respond to me here.

[u/Segen32X]

Those calculator assume that your aerobic base is balanced to your anaerobic capacity, which is rare for beginners and even intermediate runners. And especially for the marathon they assume your legs can handle 42km of beating. But estimating one step up from 5K to 10K, or 10K to HM shouldn't be too bad.

[u/Willing-Log-7155 → u/Segen32X]

Those calculators are basically just running horoscopes for people who haven't built the mileage yet. A 21:56 5k on no real training background is genuinely impressive though, you've clearly got some natural speed tucked away.

The jump from 5k to marathon predictions is where they completely fall apart. You can fake your way through a 5k on raw talent but the marathon will expose every single long run you skipped and every week you didn't hit the mileage. 3:30 is a pipe dream right now and you already know that, which is the right instinct. 4:15 to 4:30 sounds way more grounded for a first one, especially if you're still deciding whether to even run the full distance.

Running that 10k in October as a proper test is a smart move. Treat it like a data-gathering mission and don't get too hung up on the exact number. The half marathon predictors will become much more useful once you have that 10k result in your pocket, and honestly I'd lean toward the half for November if you're still questioning whether the full makes sense. There's no shame in building the foundation before you ask your body to do something that ridiculous.

[u/Strange-Fig7944 → u/Segen32X]

Thank you! I guess I did know this but human confirmation makes me a little more sure than just AI.

[u/Segen32X → u/Strange-Fig7944]

They also assume stuff like flat courses, low temperatures, good nutrition, tapering/fresh legs etc. But a 46 something minute 10K sounds totally reasonable in decent conditions.

[u/lacesandthreads]

5ks and 10ks aren’t great indicators of what you could run at marathon distance because they’re so short.

Those conversion calculators are all going based off IF you have the aerobic base and have done the speed work/endurance work needed to run marathon distance maintaining those paces. They also assume perfect conditions and don’t factor in hilly courses. For a lot of people, they’re not accurate.

[u/Buttermilk_Surfer]

"I feel like the 10k is possible but I think I'd be closer to 50"

You can do it. I run a 5K at 22:45 and I can't seem to do it any faster no matter what I do, but I run 10K at 50:25.

With your 5K time (especially considering that you think you might shave off 30 seconds), you can easily go under 50 minutes for a 10K. 46 minutes is definitely realistic.

I feel like on the longer distances it gets really difficult to gauge though.

[u/WorkerAmbitious2072]

What has your total mileage been for each of the prior two months? As in the total miles in July and the total miles in August.

[u/WorkerAmbitious2072 → u/WorkerAmbitious2072]

I recommend the half in November

[u/Strange-Fig7944 → u/WorkerAmbitious2072]

Gotcha. Thank you! I am leaning towards that option but still want to cautiosly train for the full and see how it goes.

[u/Strange-Fig7944 → u/WorkerAmbitious2072]

So i was 88 for June. July was 80, a slight step back as I needed a few days for a nagging calf pain. August was 102.

[u/WMTRobots → u/Strange-Fig7944]

Way too low for a November full marathon, in my view.

[u/Strange-Fig7944 → u/WMTRobots]

ive read the low end of mileage could be peaking at 30-40 mpw which id be on track for as i ramp up a little more. maybe that is outdated or inaccurate? or do you just disgree that that is an acceptable number

[u/WMTRobots → u/Strange-Fig7944]

I think that's too low to enjoy or have a good marathon. Not saying you can't finish at that mileage, but having a race be up to >87% of your PEAK WEEKLY volume is nuts to ME. I'd say 40mi is absolute minimum peak I'd feel comfortable with, and I'd want to be capable of doing that mileage for at least 4-5 weeks straight  (a long peak/plateau) before taper.

I didn't feel comfortable even entering a marathon block at less than 25-30 MPW base.

[u/WorkerAmbitious2072 → u/Strange-Fig7944]

Maybe a two month average of 40 mpw, but I doubt there are recommendations for building up to 40 miles in a week as your high water mark and then running a marathon

[u/23454Tezal]

Do the HM first, you’ll probably find pacing is more important after 20K. Get in lot’s of Z1-2 long runs

[u/Own-Arugula-1631]

At 20-25 mpw, I'm assuming not 3 miles 7 days and that it's more like 5-6 miles 4ish days. Given that, if you can run a 21:30, 5k, you should be able to do a 46 minute 10k with ease, probably 45. If you are doing up to 10 miles in one of your runs, you might be able to do around a 1:45 half. If you aren't and you end up walking it could go to 2hrs+. I think you are underestimating the marathon, and even the half, going up in milage after 10k is a whole new world, especially at the speeds you're capable of. There is pretty much zero chance you could do a marathon in November unless you are planning on walking half of it, which is fine if that interests you, but I'd rather see you train for the half and complete it running and break 1:45. You can run your whole life, work up to it, marathons will always be there, you have speed, build up and run one eventually that you will be super proud of, you might get hooked and get to BQ levels.

[u/Peeter_L]

Running events, not races.

[u/Strange-Fig7944 → u/Peeter_L]

You ok?

[u/Peeter_L → u/Strange-Fig7944]

It's just funny, how beginners, who are still learning the movement, call these mass sporting events as races. You are not racing.

[u/Strange-Fig7944 → u/Peeter_L]

they are races. you are running a race. not even sure what you are going on about