What time is realistic for my first marathon?
I started running last October 2025 and decided that I want to do my first marathon in January 2027! What is a realistic goal time I should train towards and when should I start my training block/start increasing mileage?
For context, I’m 26 y/o female and never ran more than 2-3 miles before October of last year. I never played sports competitively and the only fitness background I have prior to running is going to the gym consistently (been going for over a year now). I signed up for my first 10k in December 2025 and did a 8-week training block through Runna & ran my first 10k in 54 minutes. At the time, I ran only twice per week in October-December but after my first race, I started taking running more seriously. By February 202), I started running 4x per week and structured all of my runs (1 tempo/track, 1 long run, 2 easy). Since then, I’ve ran 20-25+ mpw consistently aside from reload & race weeks. By April 2026, I ran my second 10k and cut my time down to 47 minutes & ran my first half marathon at the end of May 2026 where I ran 1:41! During the half marathon training block, I peaked at 33 miles for 2 weeks in a row, but mostly ran \~25 mpw for the two months prior.
Since my half marathon, I’ve continued to run 20+ mpw to maintain and started biking/swimming as well since I signed up for my first triathlon in August. I’m thinking about starting my marathon transition block after the triathlon and want to build from 20-25 mpw to hopefully 45-50mpw (gradually increasing \~10% per week). Is this a good plan? If I started my marathon block at end of August, I’ll have 18 weeks plus an extra week to deload. Or should I start increasing mileage earlier?
Based on this information, what goal time should I train for as well? My overall first goal is to finish the marathon and I have a second goal of subbing 4 hours, which I feel somewhat confident that I can so as long as I increase my weekly mileage as planned. But I’d like to set a third “timed/competitive” goal. Maybe sub 3:45? 3:35? I further plan to run another half marathon in October with the goal of sub 1:35 as another factor to consider. Is 45-50mpw with a peak of 55-60mpw enough or should I aim for more weekly mileage? I just don’t want to overdo it as I’ve been running for less than a year and go to PT for lower leg strengthening as I previously dealt with mild shin splints when I started running.
Appreciate any suggestions ahead of time, thank you!