Your Pace
Predicted Race Times
Training Zones
Whether you are training for your first 5K or aiming for a Boston Marathon qualifying time, understanding your running intensity is the single most important factor in your progression. The runworks calculator is designed to take the guesswork out of your training by providing scientifically-backed pace targets.
The Science of Running Paces
Training isn't just about "running hard." To improve efficiently, you need to target specific physiological systems. By inputting a recent race result into our calculator, you can determine exactly how fast you should be running during different types of workouts.
Aerobic Foundation (Easy Paces)
Most runners make the mistake of running their easy days too fast. This leads to "gray zone" training—too hard to recover, but too slow to provide a high-end aerobic stimulus. Your easy pace should feel conversational. According to the runworks algorithm, this usually falls between 65% and 75% of your maximum heart rate.
Lactate Threshold (Tempo Paces)
The lactate threshold is the intensity at which your body begins to produce lactic acid faster than it can clear it. Training at this "comfortably hard" pace improves your endurance and allows you to maintain a faster speed for a longer duration. This is the "bread and butter" of half-marathon and marathon training.
How Race Predictions Work
Our calculator uses the Riegel Formula to predict your potential at other distances. The formula assumes that a runner's speed decreases at a predictable rate as the distance increases. While no formula is perfect, it provides a realistic "ceiling" for what you can achieve if you have done the appropriate mileage for the target distance.
- Input Accuracy: Use a recent race time or a time trial performed under good conditions.
- Specificity: A 5K specialist might underperform the Marathon prediction if they haven't built the necessary long-run endurance.
- Environmental Factors: Remember that heat, humidity, and elevation will significantly impact your actual pace vs. the calculated pace.
Integrating Paces into Your Schedule
Once you have your numbers from the runworks calculator, how do you use them? A balanced week typically includes:
- 80% Easy Running: Building the engine and recovering.
- 10-15% Threshold Work: Tempo runs or long intervals.
- 5% Speed/Intervals: High-intensity work to improve running economy and VO2 max.
By sticking to these zones, you minimize injury risk while maximizing performance gains. Stop guessing and start training with precision.