Why "minimum" matters more than "ideal"
Most articles tell you the ideal weekly mileage for a half marathon is 30 to 40 miles. That number is true for the median runner with a clear schedule and zero injury history. It's a useless answer for everyone else. The more honest question is: what's the floor I cannot cross without showing up to the start line under-prepared?
This calculator answers that. Pick your race, pick your goal (finish, finish strong, or compete), and we return the minimum weekly mileage you need to start training, the peak you should hit before taper, and how many weeks it takes to get there from your current volume.
How the floors are set
Values come from Jack Daniels' Daniels' Running Formula, Pete Pfitzinger's Faster Road Racing and Advanced Marathoning, Brad Hudson's Run Faster, the Hanson Brothers' marathon method, and Jason Koop's Training Essentials for Ultrarunning. The "finish" tier is set deliberately low so beginners don't get hurt. The "compete" tier is set higher than most beginner-friendly calculators because age-group runners need it. Half marathon "finish" is 25 mi/wk, not 20. Pfitzinger flags volumes under 25 as injury-prone for the 13.1 distance.
How the ramp works
From your current mileage, we build a four-week mesocycle: three build weeks at +10% each, then a cutback at -10% of the last build. The cycle repeats until you hit your peak. It's the ramp rate that reliably keeps injury risk down while still building fitness, which is why almost every coaching plan uses some version of it.
When to recalculate
Recalculate when you change your race, change your goal tier, miss two or more weeks, or come back from an injury. Mid-block, the original numbers hold.
Minimum Weekly Mileage Calculator
Tell us your race and goal. We return the floor mileage you need to start a plan, the peak you should build to, your long run range, and a week-by-week ramp from where you are today.
FAQ
Is 20 miles a week enough to train for a half marathon?
For an absolute beginner just trying to finish, 20 mi/wk is a survival floor — you can complete the distance but risk a rough final 5K and elevated injury risk. The safer recommendation is 25 mi/wk minimum, which Pfitzinger and Hudson both flag as the point below which most runners struggle to build the musculoskeletal resilience that 13.1 miles requires.
How many miles per week do I need for a marathon?
Just to finish: 30 mi/wk is the established floor (the Hansons plan starts here). Mid-pack finishers running sub-4:00 are usually averaging closer to 45 mi/wk. Competing for age-group placings starts around 65 mi/wk, with peak weeks pushing 78. Below those numbers, the long run does most of the work and you arrive at the start line under-prepared.
Why does the long run cap at 16 or 22 miles?
Long runs over 3 hours produce diminishing returns and steeply rising injury risk. For half marathon, 16 miles is the ceiling — anything more is just survival training. For marathon, 22 miles caps the standard plans (Hansons goes to 16; Pfitzinger to 22; Daniels rarely beyond 22). The 50K plan allows back-to-back long runs (e.g., 20 mi Saturday + 10 mi Sunday) instead of one absurd 30-miler.
What if I have less time than the ramp needs?
The feasibility check tells you. If the ramp + 2 weeks taper exceeds your weeks-until-race, you have three options: drop the goal tier (finish instead of strong), pick a shorter race for now, or pick a later race and use the time. Compressing the ramp below 10%/week is the option that gets people hurt.
Methodology
Floor values per race × goal tier come from coaching literature (Daniels, Pfitzinger, Hudson, Hanson Brothers, Koop). Peak = floor × variable multiplier (1.5× for floors below 30 mi/wk, 1.35× for 30-50, 1.2× for 50+). Long run = 20-30% of peak for 5K-half, 25-33% for marathon, 30-40% for 50K (with back-to-back logic). Ramp is a 4-week mesocycle: 3 build weeks at +10%/week, 1 cutback at -10% of the prior build.
Want to verify the math?
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