How to Build Your Mileage Base

What’s Included?

  • Why does increasing your mileage help you as a runner?
  • When is the best time to increase mileage?
  • How do you do it?


Increasing your baseline weekly mileage (the number of miles you typically run each week) can have a number of benefits – increased endurance, improved aerobic capacity, increased efficiency, and better running form & mechanics.

But why is this?

Let’s say a runner typically does about 10-12 miles per week but slowly increases to 20 miles per week over the course of several months. After sustaining that mileage of 20 miles per week for several weeks, how might that runner feel doing a 10 mile week? It would feel EASIER because their body is now used to doing 20 miles per week, right?

This is because the runner has now expanded their aerobic capacity. When you increase your mileage, your body can handle further & faster miles with more ease. A solid base can also help to support you when doing intense runs or workouts (think of it like a stack of blocks – the bigger the BASE, the higher one can build it).

While increasing your mileage base can have a number of benefits, it’s important to make sure you’re doing so in a way that’s safe and sustainable. Keep reading to learn how you can increase your running base safely.


Typically, a runner’s “off” season is the best time to increase mileage (typically during the Winter or the Summer) or just any time when you just know you don’t have any big races coming up in the immediate future (the next few months). Increasing your mileage during an “off” season is best because during this mileage increase period (typically 1-3 months), you’ll be doing almost exclusively easy miles. This will help you build that strong base from which you can start mixing speed work into during your training season.


Like most things in running, there’s no “one size fits all” and that’s because we are all SO very different. We all come into this with different goals, experience, fitness levels, training availability, strengths, weaknesses…. the list goes on and on. However, when you are building mileage, there are a few important tips that can help guide you:

1.) Follow the 10% rule (but loosely):

The 10% rule refers to the rule of increasing your mileage by “no more than 10%” each week to maintain safety. For example, if someone ran 20 miles on week one, they would run no more than 22 miles the following week. This is a general rule of thumb & beneficial use of it can depend upon your experience level – so keep in mind that it’s NOT a rule, it’s a guideline. For more experienced runners or runners who are returning to a higher mileage that they’ve previously maintained before, you may be able to build a little quicker.

2.) Choose a strategy that works for you:

There are endless ways to break down the increases in mileage each week – increasing your running frequency or how often you run (going from 3 days per week to 4 days), increasing your long run distance each week, or increasing all of your runs by a small amount each week. It’s okay to experiment to see what feels best for you – and it’s also okay to use different strategies each week. Just remember – you’ll want to increase by about 10% each week.

3.) Include down weeks:

Down weeks, otherwise known as cutback weeks, are defined as a week where mileage and intensity is cut back to prioritize rest and recovery before continuing to build. Mileage should typically be reduced anywhere from 15-50%. There should be at least one down week for every 2-3 weeks of hard work or building. This is important year-round, but it is especially important when attempting to build mileage or fitness. Every few weeks, a runner should take a down week to focus on rest and recovery, as well as to avoid burnout and injury.

4.) Pay attention to how hard you’re going:

Your runs during this base building phase should be in this easy zone until you get comfortable with the
mileage. Your easy pace should feel like a 1-4 RPE and should be anywhere between 60-75% of your max heart rate. You can find your max heart rate by taking your age and multiplying it by .7 and then subtracting this number from 207. For example, a 25 year old would take 25 x .7 = 17.5. Then 207 – 17.5 = 189.5 max heart rate. The easy pace heart rate would be 60-75% of this, which would be 113 – 142 heart rate. If you find that your heart rate frequently creeps above YOUR range, slow down.

Looking to build mileage and not sure where to start?

Check out our mileage builder plans to see if we have one that would be a good fit for you!

Amy Haas
Run with Aim, LLC
UESCA Certified Running Coach
NASM Certified Personal Trainer
NASM Certified Nutrition Coach