Free Zone 2 Calculator: MAF Method + Beyond

If you’re interested in building your aerobic base, I’ve put together a free zone 2 calculator that you’re more than welcome to use. 

Zone 2 training (also referred to as MAF training, base building, steady state cardio, and probably many more names that I’ve missed) is an increasingly popular training modality aimed at helping to build our aerobic capacity.

As well as supporting our general health and wellbeing, it’s a tool we can use to improve our performance in a wide range of sports and physical activities, from running marathons to having more energy to keep up with grandkids. 

I’ve put together an indepth guide one zone 2 trainingthat you;re welcome to check out, but if you;re just after the free calculator, scroll on down, plug in your numbers, and you;re ready to go. 

I’ve also included some more subjective measures you can use to roughly determine your heart rate zones if you don’t have acces to (or don;t particularly want to use) a heart rate monitor. 



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Free Zone 2 Heart Rate Calculator

There are numerous different formulas and calculators we can use to approximate our heart rate training zones. I’ll touch on some of them below, but the one I default to using is the Maximum Aerobic Function formula devised by Dr Phil Maffetone.

Early into his career as a running coach, Maffetone observed that at a certain heart rate threshold, his athlete’s running technique would start to break down. Later research helped him determine that this number approximated the upper limit of aerobic functioning in the body – the point at which we begin to use more of the anaerobic energy systems for ATP synthesis and energy production. It’s this same threshold at the upper end of your heart rate zone 2. 

The base formula for determining this number is:

MAF/Zone 2 HR (bpm) = 180 – your age

Take this number, and perform your zone 2 training sessions keeping your heart rate at or 10bpm below this threshold value. Phil recommends then adjusting this value based on criteria relating to your general well-being and training performance. 

Rather than going into too much detail, I’ve set up a free zone 2 calculator that you can plug your numbers into below:

For me, this equates to:

180-32 = 148

I could then take off 5 for inconsistent training, and even subtract another 10 because I’m recovering from long covid and chronic pain syndromes.

This gives me a rough training range of 133-143 depending on what subtractions I make, with a warmup and cooldown 10bpm lower, in the range of 123-133.

These MAF numbers seem to correlate quite well with what we’d class as Zone 2 training, but there can be some differences.

One thing to note is that for older athletes, the formula doesn’t seem to hold up as well as you approach your 50s and 60s – particularly if you have a long training history.

Decorated triathlete and MAF proponent Mark Allen suggested:

  • If you are over about 55 years old or younger than about 25 years old, add another 5 beats to whatever number you now have.
  • If you are about 60 years old or older OR if you are about 20 years old or younger, add an additional 5 beats to the corrected number you now have.

It’s also important to note that the MAF formula is just one part of the whole system called the Maffetone Method, which encompasses nutrition, training and stress management.

Other Ways to Calculate Zone 2 Heart Rate

The MAF 180-your age formula is my preferred method to calculate Zone 2 if we’re going by heart rate as it incorporates lifestyle factors that can impact our training.

But there are other ways to approximate the appropriate training intensity. We’ll go through some of the main ones below, using my heart rate numbers to compare the outcomes. 

I’ll also then share some tips for using low intensity aerobic training without having to mess around with heart rate monitors whatsoever. 


1 – The Haskell & Fox Age Regression Formula:

Max HR = 220 – age

Zone 2 training range = 60-70% Max HR

These first two formulas are based on taking a percentage of our approximated maximum heart rate.

This is considered a somewhat crude and arbitrary way to calculate zone 2 and doesn’t hold up well when we compare it to actual real-world maximum heart rates.

Based on the above:

My max HR = 188

Training range (60-70%) = 113-132 (around 10 beats lower than MAF).

2 – Robergs & Landwehr Formula:

A potentially more accurate version of the above isto use a different estimation for maximum heart rate:

Max Hr = 205.8 – (age x 0.685)

For me, this gives a max HR estimate of 184, and a suggested training range of 10-129 – again, quite a bit lower than my adjusted MAF range.

3 – Lactate Threshold Formula:

Here, you’d perform a test to figure out your approximate lactate threshold, then your Z2 heart rate would be around 80-90% of that value.

This often gives a higher Z2 range than the max heart rate calculation and for me, it looks a lot more like my MAF numbers.

The downside is you have to  perform a lactate threshold test, which is not fun. Some fitness trackers will approximate your lactate threshold, but they’re not typically the most accurate.

4 – Heart rate reserve (HRR) and the Karoven formula:

Target Heart Rate Intensity Zone = ((max HR − resting HR) × %Intensity) + resting HR.

This is potentially a more accurate approximation as it takes into account resting heart rate which is an indicator of aerobic fitness.

It’s not perfect, but some people find it feels more in line with their actual experience.

For me, the value comes out at 130-145 – right in line with my MAF numbers.

5 – The Breathing Gears System

If you don’t fancy fussing around with a heart rate monitor, the breathing gears system devised by Brian Mackenzie and the team at Shift Adapt may be the route for you. 

Instead of using heart rate, you’re judging your training intensity based on you breathing pattern.

  1. Gear 1: equal nasal in // out – low aerobic
  2. Gear 2: power nasal in // nasal out – high aerobic (Zone 2 / MAF)
  3. Gear 3: power nasal in // power nasal out – anaerobic threshold
  4. Gear 4: nasal in // mouth out – low anaerobic
  5. Gear 5: mouth in // mouth out – high anaerobic

As we can see from the above, if we’re able to maintain nasal breathing, it’s likely we’re predominantly within our aerobic heart rate zones. Another metric to use is whether or not you an hold a conversation with relative ease.

This is actually the system that I now tend towards, as it means I get less caught up with what my watch is telling me, and I’m instead more in tune with my body. I still have a rough idea what my zone 2 or MAF heart rate range is, but I’m not completely caged by it. 

Key Takeaways

The most important takeaway: no formula based on simple metrics like your age is going to be 100% accurate on an individual level.

We’ve made many attempts to quantify and put things into neat boxes, but ultimately there’s no definitive answer as there are just too many variables there to account for.

You can use the above zone 2 calculators, or simply experiment with going for a pace you can maintain a conversation at, with comfortable, nasal breathing.

There’s no perfect answer here – find what feels good for you.

When I’m out on a slow, easy run, I find I’m closer to my MAF heart rate. When I’m doing weighted walking or rope flow, I’m typically at the lower end of the MAF range, which may be more akin to the Z2 calculated off HRMax.

It doesn’t have to be one or the other – it’s not a perfect science.

There are also other things that can impact how intense a training session feels and how challenging it is on your body on the day – sleep, nutrition, recovery, genetics, health status. Going into a session thinking I have to hit these predetermined numbers might not be the smartest way to train.

The principles behind Z2 and MAF training are pretty much the same, to build your aerobic base through easy, low-intensity training. It doesn’t have to necessarily be more complicated than that, and as we can see from this article, getting caught up in the details doesn’t necessarily help us.

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Luke Jones

Luke Jones is a Movement Coach, Wellness Enthusiast, Online Content Creator, and Founder of HERO Movement. Through articles, videos, courses, and online coaching, his big goal is to help people discover freedom of movement and create lives filled with well-being & adventure.

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