The Numbers Behind Your Workout: Pace, One-Rep Max, and Heart Rate Zones
How pace, estimated 1RM, and target heart rate zones are calculated, with real training examples.
Runners, lifters, and cyclists all rely on a handful of formulas to translate raw workout data into numbers they can actually train against.
Estimating your one-rep max without attempting it
Testing a true 1-rep max is risky without a spotter and experience, so most lifters estimate it from a submaximal set using the Epley formula: 1RM = weight × (1 + reps/30). Lift 100kg for 8 reps and your estimated max is 100 × (1 + 8/30) = 100 × 1.267 = 126.7kg. This formula is most accurate under about 10 reps — high-rep sets (15+) produce less reliable 1RM estimates because muscular endurance starts influencing the number more than pure strength.
Pace: the inverse of speed
Running pace is usually expressed as minutes per kilometer or mile — literally time divided by distance, the inverse of the speed formula you might remember from physics class. Cover 10km in 50 minutes and your pace is 50/10 = 5 minutes per kilometer. Converting to miles multiplies by 1.60934 (km per mile): 5 × 1.60934 ≈ 8.05 minutes per mile.
Heart rate zones: percentages of a maximum
The widely used 220-minus-age formula estimates maximum heart rate, then training zones are calculated as percentages of that max. A 35-year-old has an estimated max HR of 220−35 = 185 bpm. Their "moderate" zone (50-70% of max) runs from 92.5 to 129.5 bpm, and their "vigorous" zone (70-85%) runs from 129.5 to 157.25 bpm. The 220-age formula is a population average with real individual variation (±10-15 bpm isn't unusual), so a lab-measured max heart rate is more precise if you have access to one.
Race time prediction: Riegel's formula
Riegel's formula predicts a race time at one distance from a known performance at another: T2 = T1 × (D2/D1)^1.06. Run 10km in 50 minutes and want to predict a marathon (42.195km)? T2 = 50 × (42.195/10)^1.06 ≈ 246.6 minutes, or about 4 hours 7 minutes. The formula assumes similar training and conditions across both distances, so it gets less accurate the further apart the two distances are.
Calculate your own targets
- The one-rep max calculator and Wilks score calculator cover strength training numbers
- The pace calculator and marathon time predictor cover running-specific math
- The heart rate zone calculator and VO2 max calculator (Cooper test) round out cardio training metrics