I´ve run 1:51 and 3:46 on 50mpw. What can I run at 5k if I double my mileage?

I'd wager you can run a 14:45 5k now but if you double your mileage you will injure yourself and only run 16:30.

I agree. He has found his sweet spot.

Stay gangsta says you can run 14:30 right now.

Don’t try to double your mileage, just continue what you’re currently doing and increase it progressively.

Agree, 100 mile week is not needed for 5k. go up to 75-80 per week and get endurance strength and your leg speed will let you blow away those 100 mile per week slower runners. 13:45 is very possible.

You should be able to run a 13:50 based on my experience. You have the perfect frame for the 5k

Maybe try asking the person who helped you get to 1:51 and 3:46 instead of a bunch of idiot strangers.

I am calling bs on the 3:46 mile.

I'm thinking you can run around 12:38 for 5000m and at least 27:00 for 10,000m

Almost certainly 3:46 1500m...

You for sure have potential going under 14:00, 3:46 and 1:51 point to a good running economy and with the info provided it sounds like you have a good build for longer distance. Going from a 50 mpw guy to a 100 mpw guy while maintaining quality workouts and recovery will take you a couple years at the least though. Try bumping up 10 mpw in 3 month cycles and see if you can find your sweet spot. Lots of people run their best at 5k in the 80 mpw give or take range and will have a hard time making it to the start line let alone the finish line if they do more.

First, consult your coach about increasing to 65 mpw. Are you doing doubles yet? You'll need to for 100 mile weeks. Maybe add a few 4 mile runs 3-4 days a week. See how your times (workout and time trial/race) adjust to the increased load. You may want to stay at this level for 6 months (with some variations depending on your cycles). Maybe then increase to 75 mpw. It should take you 2-3 years to increase to 90-100 mpw. Only increase if you can handle it and you are progressing. If you get sick often, are always tired, your times are slower for a period/season, or all the fun in running is gone: you need to discuss with your coach decreasing the volume. Your coach may not do this for you. You may have to advocate for yourself. If your coach is already only planning 50 mile weeks and not putting everyone into a one size fits all high mileage plan, there's a good chance they will personalize your plan.

You're gonna need to take it a bit slower than that. 50 -> 100 is crazy talk. Start with 60 this summer, see how that goes. If it's going well, try getting to 70 over the winter break. If that goes well, try getting to 80 next summer. Keep doing this until you find your sweet spot. For most athletes, the sweet spot for 5k is somewhere between 70 and 120 miles. There are a rare few (Lagat and Levins come to mind) that their sweet spot is outside of that range. If it's 100 for you, it will take you 2-3 years to get there (which is completely fine).

Assuming you are equally good at the 5k as the 1500, 100 mpw is your sweet spot, AND you see zero improvement in your 1500 by going to 100 mpw, you would expect to run ~13:50-14:00 for the 5k. However, I would expect at least one of these assumptions to be false, likely all three. Because of that, it's hard to pinpoint an accurate prediction. If 100 mpw is way too much for you, and you are naturally worse at the 5k, you may struggle to even get healthy enough to race, and may only run 15:00 or so. If you end up way better at the 5k than the 1500, and you see massive gains from the mileage, you could run 13:00 or even under 13:00. The most likely outcome is naturally somewhere in the middle, where you improve your 1500 to ~3:40 and run ~13:40 for 5k, but the only way to find out for sure is to attempt it.