If you don’t know your marathon pace and want to figure it out, there is an easy way to do it. A runner running 5 km faster than 20 minutes should add 20-25 seconds to the total time it takes you to run one kilometer over a distance of 5 km. If you are running slower, add about 30 seconds to your 1 km by 5 km run time. This pace will be faster than your normal pace, but also slower than for a half marathon.
Then, with your pace, you can predict the timing of your marathon using our pace calculator.
For example: your time for which you ran 5 km was 21 minutes. So your pace per kilometer is 4:12, add 30 seconds to this pace, we get 4:42 min / km, which will be your approximate marathon pace.
Add the 4:42 pace to the calculator to find out the estimated time for your marathon and get the time 3:18.
Another option if you are counting in miles:
Run one mile as fast as you can. Then, to predict your target pace for a marathon, take the time in mile (seconds) and multiply by 1.3. The result is your marathon pace per mile.
For example, you ran a mile in 6:30, decompose the resulting time into 390 seconds, and 390 x 1.3 = 507 seconds, convert to minutes and get an 8:45 min/mi marathon pace for a 3:49 marathon.
You must understand that running pace cannot be calculated and mathematically predicted 100%. Fatigue, weather and climb will affect your pace.