Selecting methods
We use recognised equations and training methods when they suit a calculator's purpose. We favour methods that are widely used in sport, straightforward to explain, and useful for practical planning. Each formula or model is chosen because it has reasonable support in sport science literature and is commonly referenced by coaches and practitioners.
Where multiple valid methods exist, we select one that balances simplicity and usefulness. For example, the Epley equation for 1RM estimation is simpler than some alternatives but produces results consistent with other validated prediction models across the rep ranges most lifters use in training.
Formula selection examples
- Rowing watt-to-split: Uses the standard Concept2 pace-power relationship. This is the same model used by Concept2 ergometers and is widely accepted in rowing for both erg and on-water pacing estimates.
- Running race prediction: Uses the Riegel distance-time model (T2 = T1 × (D2 / D1)^1.06). This model has been used in endurance running for decades and provides a practical starting point for goal setting across common race distances.
- Strength estimation: Uses the Epley formula (1RM = weight × (1 + reps / 30)). Validated against actual 1RM testing for submaximal sets up to approximately 10 reps, making it suitable for everyday training load planning.
- Nutrition targets: Uses the Mifflin-St Jeor equation for resting energy expenditure, adjusted with activity factors and goal-based calorie modifications. Mifflin-St Jeor is among the more accurate BMR prediction equations for the general adult population.
How results should be interpreted
Calculator results are estimates, not measurements. They are based on mathematical models that simplify real-world physiology and performance. The accuracy of any result depends on the quality of the inputs and how closely the individual matches the assumptions of the underlying model.
We recommend treating calculator output as a starting point or reference range, then adjusting based on personal experience, training feedback, and professional guidance where appropriate.
Limits and context
Inputs, testing conditions, training history, fatigue, terrain, technique, and individual physiology all affect real outcomes. A calculator result is not a guarantee or diagnosis. Use it as one input alongside coaching, recovery, and observed performance.
Performance prediction models have inherent limitations. For example, the Riegel formula assumes a constant fatigue exponent that may not apply equally across all individuals. The Epley formula becomes less reliable at higher rep ranges. Nutritional estimates cannot account for individual metabolic variations, medical conditions, or the thermic effect of specific foods. Understanding these limitations helps users apply results appropriately in their own training context.
Using results in practice
The most effective way to use these calculators is to combine the numerical estimate with qualitative feedback. For example, if a race time predictor suggests a 5K goal of 19:30, test that pace in a training session and assess whether it feels sustainable, too aggressive, or too conservative given your current form and conditions.
We encourage users to track results over time rather than relying on a single calculation. Trends — such as improving 1RM estimates or faster predicted race times — are more meaningful for performance assessment than isolated numbers.