How to use this long run pace calculator
Enter the requested distance, time, pace or speed, then select Calculate result. The calculator preserves seconds before rounding the displayed answer, which avoids the errors that build up when pace is rounded too early. This is especially useful for building endurance while controlling accumulated fatigue.
The estimate begins with average pace from a recent 5K and applies a purpose-specific range. It is intentionally a range rather than a single mandatory number. A 5K result should be recent, accurately measured and representative of current fitness.
How to interpret your result
Treat the displayed number as a planning reference. Pace describes an average and does not show whether the effort was evenly distributed. Two runners can finish in the same time while using very different strategies. Review lap data and perceived effort alongside the final average whenever those details are available.
Training intensity should match the purpose of the session. Easy and long runs support aerobic volume; tempo and threshold work add controlled intensity. Slowing down because of heat, hills or fatigue is not a failed workout when the intended effort stays correct.
Accuracy and useful adjustments
CalcFino uses full-precision conversion factors and rounds only the final display. Your input quality remains the largest source of uncertainty. GPS distance can drift around buildings, under trees and on tight tracks. Certified race distances, calibrated treadmills and correctly measured pools provide stronger inputs.
Weather and terrain change sustainable pace even when fitness is unchanged. Heat increases cooling demand, wind changes energy cost and elevation adds muscular load. Use the result to establish a baseline, then adjust with experience and effort. Do not use a calculator to override pain, illness or medical guidance.
Frequently asked questions
What is a good pace for a weekly long run?
Your weekly long run should be 10-20% slower than your goal race pace, or about 45-100 seconds per kilometer slower. If your marathon pace is 5:00/km, long runs belong around 5:30-6:00/km. The primary goal is time on feet and aerobic endurance, not speed. Research points to 55-75% of 5K race pace as the optimal effort band, with the average target near 65%. Long runs should feel comfortable and conversational from start to finish.
How long should my longest long run be before a marathon?
Most marathon plans peak the long run at 20-22 miles (32-35 km). Going beyond 22 miles raises injury risk without meaningful additional aerobic benefit, because the endurance adaptations plateau around 2.5-3 hours of running regardless of distance. Hal Higdon's plans top out at 20 miles, while Pfitzinger programs reach 20-22. Beginners can safely peak at 18-20 miles. Run the last few miles at marathon pace if the plan calls for it, then taper.
How much slower than marathon pace should long runs be?
Use a 10-20% slowdown from marathon goal pace, a guideline from Pete Pfitzinger echoed by Runner's World. At 9:00/mile marathon pace, that is long runs of 9:54-10:48/mile. Runner's World's intensity recommendation sits in the same band. The first few miles should be the slowest, nearly jogging, then settle in. Faster long runs belong only in structured workouts, like the final 5-8 miles at marathon pace, not for the entire run.
How often should I do long runs?
Do one long run per week, typically on a weekend when you have time. Every 3-4 weeks, cut the long run back by 20-30% for a recovery week, which lets your body absorb the training stimulus and prevents overuse injuries. Long runs build progressively, usually adding no more than 10% of distance per week. In a 16-20 week marathon block, long runs build from about 10 miles to a peak of 20-22 miles before tapering.
What is a progression long run?
A progression long run starts well below goal pace and gradually accelerates, finishing at or slightly above marathon goal pace. For example, start the first 2-3 miles at 60-90 seconds per mile slower than marathon pace, settle to easy pace, then run the final 20-30 minutes at marathon pace. This teaches your body to run fast on tired legs, mimicking the final 10K of a marathon, and builds the mental confidence to accelerate late. Do them only in the back half of a training block.
How fast should the first mile of a long run feel?
The first mile of a long run should feel almost painfully slow, like an easy jog or shuffle. Most coaches recommend taking the opening 1-2 miles as a warm-up, 60-120 seconds per mile slower than your average long-run pace, then gradually settling in. This conserves glycogen, warms up the muscles and cardiovascular system, and ensures the middle of the run is not slower than the start. Many runners make the mistake of starting at target pace and fading.
Should I fuel during long runs?
Yes, for runs longer than 75-90 minutes. Practice taking in 30-60g of carbohydrates per hour, from gels, chews, or sports drink, starting before you feel depleted rather than after. This trains your gut to absorb fuel during the marathon and prevents glycogen depletion in the final miles. For runs over 2.5 hours, aim for the upper end, 60-90g per hour. Always rehearse your exact race-day fueling plan in training, never experiment on race day.