Pace Calculator

Pace is the time it takes to cover a unit of distance, usually given in minutes per mile or minutes per kilometer, and it is how most runners think about effort. Speed expresses the same thing the other way round, as distance per hour. Enter any two of time, distance and pace above and the calculator solves for the third. For example, 5 miles in 50 minutes 25 seconds is a pace of 10:05 per mile, or about 6:16 per kilometer.

Typical Races and World Record Paces

Road and track races are run over standard distances, and the table lists the men's and women's world records for several of them with the average pace each one requires. Records are as ratified by World Athletics as of 2025 and may since have been broken. For comparison, recreational runners commonly finish a 5K at about 9 to 12 minutes per mile and a marathon at 10 to 12 minutes per mile.

Pace = time ÷ distance · Time = distance × pace · Distance = time ÷ pace

Speed is the inverse of pace: a pace of 8:00 per mile is 60 ÷ 8 = 7.5 mph. One mile is 1.609344 km, so pace per km = pace per mile ÷ 1.609344.

Training Through Pace and Heart Rate

Pace tells you what you are doing; heart rate tells you what it costs your body. Training at a planned mix of easy and hard paces, and checking heart rate to confirm the effort, helps you build endurance steadily while avoiding the common mistake of running every session at the same moderately hard effort.

Measuring and Estimating Heart Rate and Heart Rate Zones:

You can measure heart rate by counting your pulse at the wrist (radial artery) or the side of the neck (carotid artery) for 15 seconds and multiplying by four. Chest-strap monitors give the most accurate readings during exercise; wrist-based optical sensors are convenient but can lag or misread during intervals.

Training zones are usually set as percentages of maximum heart rate (MHR). The simplest estimate is 220 minus your age, so a 30-year-old would have an estimated maximum of 190 beats per minute. The Tanaka formula, 208 − 0.7 × age, is a little more accurate for older adults. Both are population averages, and an individual's true maximum can differ by 10 to 15 beats or more, so a supervised exercise test is the only way to know yours.

The American Heart Association describes moderate-intensity exercise as roughly 50% to 70% of maximum heart rate and vigorous exercise as 70% to 85%. Many coaches split this into five zones: very light recovery work at 50% to 60%, easy aerobic running at 60% to 70%, steady aerobic or marathon-pace effort at 70% to 80%, threshold work at 80% to 90%, and short, maximal efforts at 90% to 100%. Another approach, the Karvonen method, applies the percentages to heart rate reserve (maximum minus resting heart rate) and then adds the resting rate back, which personalizes zones for people with very low or high resting heart rates.

Heart rate is affected by heat, dehydration, caffeine, stress, illness and lack of sleep, so the same pace can feel and measure harder on some days. If you take medication that affects heart rate, such as beta blockers, ask your doctor how to judge intensity.

Aerobic vs. Anaerobic Exercise:

The body makes the energy for movement, in the form of ATP, through different pathways that work together but dominate at different intensities.

Aerobic exercise is activity at an intensity where the heart and lungs can deliver enough oxygen to the muscles to meet demand. The muscles then produce energy mainly by burning fat and carbohydrate with oxygen inside the mitochondria. This process is efficient and can be sustained for a long time, which is why easy running, brisk walking, cycling and swimming can continue for an hour or more. You can usually talk in full sentences at an aerobic effort.

Anaerobic exercise is intense enough that energy demand outstrips oxygen supply. For the first few seconds the muscles rely on stored ATP and phosphocreatine, which power sprints, jumps and heavy lifts. Beyond that, they break down glucose without oxygen (anaerobic glycolysis), which is fast but produces lactate and hydrogen ions. The burning feeling and rapid fatigue of hard intervals come mostly from the build-up of these by-products and other changes in the muscle, not from lactic acid itself causing damage. Anaerobic efforts can only be held for seconds to a few minutes.

The boundary between the two is not a switch. As pace rises, more energy comes from carbohydrate and more lactate is produced. At the lactate threshold, lactate starts to accumulate faster than the body can clear it; for trained runners this is roughly the pace they could hold for about an hour. Above it, fatigue arrives quickly. The highest rate at which your body can use oxygen is called VO2 max, a key measure of aerobic fitness that improves with training and declines with age.

Both types of exercise build fitness in different ways. Aerobic training strengthens the heart, increases the number of capillaries and mitochondria in muscle, improves the body's ability to burn fat and lowers resting heart rate and blood pressure. Anaerobic training, such as intervals, hill sprints and strength work, builds power and speed, raises the lactate threshold and helps maintain muscle and bone. Most endurance programs combine them: a large share of easy aerobic running, often around 80% of weekly time, with smaller amounts of threshold and interval work.

For general health, the CDC recommends that adults get at least 150 minutes of moderate aerobic activity, or 75 minutes of vigorous activity, each week, plus muscle-strengthening activities on at least two days. Increase training volume gradually, about 10% a week is a common guide, to lower the risk of overuse injuries, and include rest days so the body can adapt.

Frequently asked questions

Sources

• CDC – Physical Activity Basics
• American Heart Association – Target Heart Rates
• World Athletics – Records