How to Predict Your Marathon Time

Ahh, don’t we all wish we could have a crystal ball that was a marathon time predictor. But then, what fun would that be?  Part of not knowing how we will perform in our marathon is part of what draws us. Yet, in the heart of my marathon training cycle, I find myself starting to obsess over trying to predict my marathon time and marathon race pace. (The athletes I coach do this, too.)

I remember in my marathon build in 2019 when I was trying to qualify for the Olympic Trials, I began to pester anyone who knew anything about my running what they thought—could I do it? Could I run a sub-2:45 marathon time?

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I repeatedly asked my husband, my running friends, and my running coach. I feel certain it was obnoxious and annoying. (Thank goodness they didn’t ditch me after this!)

Related: How to Prepare for Your Marathon

The truth is while there is no crystal ball that can predict marathon times, there are signs in your training that can help you determine what time it will take you to run a marathon.

Why Marathon Predictors are Inaccurate

If you search for “how to predict my marathon time” or “how to predict marathon race pace” a lot of “tricks” will show up including overly simplified workouts and marathon time prediction calculators. But to be honest, most of these are very inaccurate and misleading.

There are a lot of variables that go into training for a marathon that go beyond speed and endurance. You also need to know your fatigue resistance, lactate threshold, fueling capabilities, not to mention the course, race vibes, and weather, to name a few.

Related:How to Recover from Hitting the Wall

A lot of these marathon prediction calculators and workouts don’t take this into consideration—because it’s hard! Looking at these to guide your marathon race pace strategy is not unlike shaking a magic 8 ball. It’s pretty random and not based on relevant facts.

So, how do you predict your marathon time?  How can you know what your marathon race pace should be? There are a number of ways to highlight clues as to what you will run on race day.

I got with esteemed running coach, Laura Norris, who knows a lot about marathon predictions and pacing from her experience and research studies.

Norris has coached hundreds of athletes and errs on the side of caution. (Because those who overestimate their marathon finish times tend to go out too fast and blow up! It’s much better to underestimate and have a big kick in the last 10k)

In this article, I will cover:

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• What is a realistic marathon time
• Can I train for a specific marathon time
• How to predict your marathon time according to workouts
• What marathon prediction calculators are the best
• If the Garmin race predictor is accurate
• How to use races to predict your marathon time
• Can you use your easy pace to predict your marathon time, plus
• Key takeaways of how to predict your marathon performance

Remember: All these marathon prediction strategies are a guide, they are not the rule.

Ok, let’s roll!

Related: 9 Mental Training Tips from Sports Psychs

What is a realistic marathon time?

A realistic marathon time is relative to you and your training. For example, if you’re new to running, choosing to run a sub-4 hour marathon in your first marathon is likely unrealistic unless you have phenomenal talent.

If you’ve run several marathons successfully and are choosing a goal that’s within five minutes of your most recent marathon time, that may be more realistic.

However, the faster your marathon time gets, the harder it is to shave off time. Newer runners will see bigger bumps in their marathon times as they become more consistent with running.

Related: 7 Marathon Recovery Tips to Recover Faster

Can I train for a specific marathon time?

You can train for a specific marathon time if it’s reasonable.

We, runners, love choosing goals and going for them. This is admirable. What’s not admirable is setting lofty goals that set us up for failure.

As Norris puts it, we are not robots. We cannot input a pace and then just beat our bodies into learning how to run at that pace.

Instead, we need put in the work that allows our bodies to adapt to run at that pace. We must progress from WHERE WE ARE. There is no forcing fitness. No shortcuts. As Norris so eloquently says, “there’s no reverse engineering” in running.

So, when choosing your goal marathon time, make sure it is within reason of your current fitness and how much time you have to train.

How can I know my predicted marathon time and marathon race pace?

You can know your predicted marathon time by looking at your long-run pace and your workout paces. A lot of the below methods of determining your marathon time expect you to have a ballpark idea of where your marathon finish time may be.

If you have run workouts or races, you can plug these times into a race pace calculator or race estimator to determine a ballpark of paces.

Related: Scientific Benefits of a Long Run

If you have no idea what your paces will be, you can expect your long run pace to be close to your marathon race pace.

This strategy is most appropriate for those who are running their first marathon, wanting to complete the marathon with no time goal, and/or will run a marathon at or above 4 hours and 15 minutes (long run paces exceed 9:45 a mile).

You need to be honest with yourself with estimating your marathon time. For example, your long run pace is 10 minutes per mile and you feel exhausted after running or don’t feel like you can run much faster, then a sub-4 hour marathon is not a realistic goal.

When is the best time to predict my marathon time?

The best timeframe to predict your marathon time is about 2 to 3 weeks ahead of your marathon. This is because by this time, ahead of your marathon taper, most of your fitness is already built.

You will gain some fitness and have fresh legs to carry you the extra miles in the marathon. But by this time, you should have enough threshold and marathon pace workouts to have an idea of what pace you can hold for 26.2 miles.

How to Use Workouts to Predict Marathon Times

Workouts that simulate a marathon are best to predict your marathon time. These workouts include lactate threshold runs and marathon pace workouts. You can use the following marathon workouts to gain fitness and better estimate your ability.

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Related: What is a Tempo Run?

What workouts help you predict your marathon time?

Threshold and marathon pace workouts as part of a long run do a great job of preparing the body for running a marathon and give you an idea of what your marathon race pace may be.

Related: What is Rate of Perceived Exertion? & How to Use It in Training

The below workouts from Laura and me are most accurate for those who can probably run a 4 hours and 15 minute marathon or faster (a 9:45 mile pace or faster).

• Long run marathon pace workout marathon pace 4, 3, 2, 1: Warm up for 2-3 miles then do 4 miles at an RPE (rate of perceived exertion) of 5-6/10, 1 mile easy, then do 3 miles at an RPE of 5-6, 1 mile easy, 2 miles RPE 5-6, 1 mile easy, then 1 mile more at RPE 5-6, cool-down for 2-3 miles. RPE of 5-6 is a moderate effort. You can speak in short sentences but not hold a conversation. The average pace for these miles plus 25-35 seconds will be a good goal marathon pace.
• Steady-state workout: Warm-up for 2-10 miles, then run at an RPE of 5-6 for 10 miles, cool-down for 1-5 miles. The average pace of this workout plus 25-35 seconds will be a good goal marathon pace.
• Threshold workout: Warm-up for 2 miles then do 3 by 10 minutes at a threshold pace (RPE 7) with a 90-second interval rest in between. Cool-down for 2 miles. The average pace of this workout plus 25-30 seconds will likely be a good goal marathon pace.

Pay attention to how you feel in these workouts. If you are struggling to hold the pace, then it’s not likely you will be able to hold this pace for 26.2 miles. Be honest with yourself. The marathon taper helps but it doesn’t work magic.

Related: How to Taper for a Marathon or Half Marathon

Workouts like the Yasso 800s do not accurately predict marathon times because they do not simulate the physiological demands of a marathon.

What are Yasso 800s?

Yasso 800s were created by Bart Yasso, Runner’s World  “chief running officer.” The theory of the Yasso 800s is that you run ten 800 meter intervals on a track. You repeat this workout several times throughout your training. When you can consistently hold a pace for all then, that correlates to your marathon time (by replacing minutes with hours).

Are Yasso 800s accurate?

No, Yasso 800s are not very accurate. The main reason workouts like the Yasso 800s or sprinting a mile and multiplying the pace (in seconds) by 1.3 to get your marathon pace (in seconds) are partly anaerobic and the marathon is an aerobic exercise. Two totally different systems in the body are working—one using oxygen and one not.

The muscle fiber typology is also different. Shorter distances like the mile and half a mile will recruit more fast twitch muscle fibers whereas endurance events will use mostly slow twitch. 

To predict your marathon time, you need to run workouts that mimic the marathon.

How to Use Race Time Predictors to Predict Marathon Times

There are plenty of race time predictors and race pace calculators that aim to predict your marathon race time or race times at other distances. Some of these marathon predictor calculators are more accurate than others.

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Bear in mind:  

• The marathon pace calculators are estimators, not an exact science.
• the longer the distance it’s predicting, the least accurate a race prediction calculator may be.
• The shorter the race distance, the more accurate the race prediction will be.
• The more well-trained, fresh and/or fast an athlete, the more accurate these race predictors will be.

What are the best marathon time predictor calculators?

According to Norris (and I agree!), the best marathon pace calculator is Jack Daniel’s VDOT calculator. However, the VDOT calculator does tend to overestimate marathon times. The fitter and faster you are, the more accurate the VDOT calculator will be.

How accurate is the VDOT calculator in predicting marathon times?

According to Norris, the VDOT race equivalency calculator is derived from data of elite runners. Therefore, it’s most accurate for those running 70 miles a week or more. And most marathoners can add minutes to their VDOT marathon prediction.

Below are estimations of what to add based on your predicted marathon time:

Sub 3-hour marathoners:

• Add 0-5 minutes to your predicted marathon time, depending on your racing profile, says Norris.
• If you have a faster half marathon than your equivalent 5k, you can 0-2 minutes. (How you feel at goal marathon pace can help you decide how much to add). If you’re better at shorter, faster distances (e.g., your equivalent half marathon time is slower than your equivalent 5k) , then you can add 4-5 minutes to your VDOT predicted marathon time.

3-4:15 hour marathoners:

• Add 5-7 minutes to your VDOT marathon prediction.
• Again, add more time if you perform better at shorter distances than longer distances.

4:15 and above marathoners:

• Your long run pace is likely close to your marathon race pace.

Is the McMillan running calculator accurate?

The McMillan calculator tends to overestimate marathon time and drastically overestimate what your easy pace should be, says Norris.

Is the Slate marathon time predictor accurate?

No, the Slate marathon time predictor is not accurate, says Norris. While this marathon race equivalency calculator aims to be accurate by adding another data point (weekly mileage), this data point can skew results.

For example, if you are a 2:05 half-marathoner who runs 70 miles per week (which is too much for someone who runs that pace, by the way!), then it will predict your marathon time much too fast. The reverse is true for someone who has a fast half-marathon but runs lower mileage such as 40 miles per week.

Is the Runner’s World Race predictor calculator accurate?

The Runner’s World Race predictor is not accurate though it does tend to mirror VDOT, says Norris. The Runner’s World Race predictor calculator also includes a weekly volume data set.

However, in my experience, this data set too heavily influences the predicted marathon race pace. The higher the volume, the (much) faster you will run, it says.

Is the Garmin Race Predictor accurate?

No, the Garmin Race Predictor feature is not accurate and tends to overestimate race finish times. The reason, explains Norris, is that Garmin is using an optical wrist monitor which can have a high margin of error to compute your predicted race times. Also, there are wide heart rate variations based on age, size, sex, and genetics, for example.

Plus, as Garmin notes “these times are just predictions and do not factor in variables including weather, course difficulty or training regimen.”

“It is essentially throwing darts at a board,” she says, noting she’s had 4-hour marathoners think they can run a 3:30 hour marathon and be very disappointed on race day.

Our advice? Pay little attention to Garmin’s race predictor.

Related: Is Garmin’s VO2 Max Accurate?

How to Use Race Performances to Predict Marathon Times

Perhaps one of the most accurate ways to predict your marathon time is to run a race and then add time to your average pace for that race. The longer the distance, the more accurate your marathon time prediction will be.

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According to Norris, you want to run a race that is at our below your critical speed (aerobic versus anaerobic exercise) which is a pace you can hold for about 45 minutes. For most runners, these are distances of 10k or longer such as a half marathon.

Related: 13 Smart Race Days Tips to Nail Your PR

Generally, says Norris, you can use the following formulas to estimate your marathon pace:

• 10k race pace plus 45 seconds per mile
• 15k race pace add 30 seconds per mile
• Half marathon add 20-25 seconds per mile

I highly recommend racing several times in your marathon cycle anyway. This gives you the race day experience which can calm race day anxiety, learn your race morning routine, and perfect racing strategies such as running tangents or grabbing water cups.

Related: How to Calm Race Day Anxiety

Is doubling my half-marathon time and adding 7 minutes accurate?

The popular equation of doubling your half marathon time and adding 7 minutes tends to overestimate fitness. Adding 10 minutes to your doubled half-marathon time tends to be more accurate. Add more minutes if your predicted marathon time is about 3 or 4 hours.

Using Easy Pace to Predict Marathon Finish Time

Can you use your easy pace to predict your marathon finish time? No, you cannot use your easy pace to predict your marathon finish time except for runners who run 9:45 minutes per mile or slower on their easy runs and long runs. This pace will likely be close to your marathon pace.

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Related: 26 Race Day Tips for Going 26.2

You will read a lot that you can subtract 1 to 2 minutes from your easy pace to get your marathon pace. This is not accurate, especially for runners who run paces north of 9:45 a mile on most runs. As Norris explains, you cannot reverse engineer your marathon pacing—for faster runners or slower runners.

For example, many sub-3 hour marathoners will run their easy runs at a 9:30 pace because they are running high volume and fast workouts.

While 4+ hour marathoners will run their easy runs at marathon pace.

For many runners, Norris notes, if your marathon pace is close to your easy run pace, that’s a signal that you should slow down on your easy runs.

Related: Benefits of an Easy Running Pace

Key Takeaways of How to Predict Your Marathon Performance

Accurately predicting your marathon performance involves looking at an arsenal of data, not just one data point. Below are key takeaways of how to predict your marathon performance:

• Jack Daniels’ VDOT calculator is the most accurate marathon time predictor but it tends to overestimate marathon times, particularly for runners who run a marathon time of 3 hours and above.
• Racing a 10k, 15k or half marathon is a great way to predict marathon performance. Add 45, 30, and 20 seconds to these paces to get a goal marathon pace.
• Threshold and marathon pace workouts based on effort can help you determine a potential marathon time.
• Anaerobic workouts and distances (short and fast) and the Garmin race predictor are not accurate ways to predict marathon finish times.
• If your long run pace is 9:45 or above, you can expect this pace to mirror your marathon race pace.
• Be honest with how you feel in your workouts and long runs. Can you hold your goal marathon pace for several hours?

Remember that race day vibes, a marathon taper boost, and fueling properly (about 60 grams of carbohydrate per hour) will help you on race day but will not supplant proper training!

Also remember, we learn something from every race, so the more marathon your run, the better!!

Related: Marathon Fueling 101

If you want guidance with your marathon training, check out my run coaching services. Also, be sure to check out my free training plans:

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