Running Calculators
Free, evidence-based tools for training, racing, and recovery
Pace & Performance
Training prescription and fitness measurement tools
Race Day Preparation
Fine-tune your strategy for race-day conditions
Body & Physiology
Measure and interpret your body’s signals
Free Scientific Running Calculators
myRunningPace offers 12 free calculators spanning pace prediction, race-day strategy, lactate physiology, and nutrition — all built on peer-reviewed sports science. From VDOT-based training zones and Riegel race predictions to Norwegian-style double threshold session planning and minute-by-minute lactate simulation, every tool turns your data into actionable insights. No accounts, no paywalls — calculations run entirely in your browser.
What Are These Running Calculators?
Each calculator implements a specific exercise science model in a user-friendly interface. The Training Pace Calculator prescribes six training zones using four models (VDOT, Riegel, Critical Speed, Hybrid). The Race Time Predictor forecasts finishing times across seven distances with confidence intervals. The VO₂max Estimator derives your aerobic fitness score from race data. Environmental tools — Heat-Adjusted Pace and Sweat Rate — model thermoregulatory stress and fluid loss. The Carb Fuel Calculator builds per-hour fueling plans for race day. Heart Rate Zone and Lactate Threshold calculators map your physiology to training intensity. The Polarized Training Calculator scores your weekly training distribution against Seiler's 80/20 model. The Lactate Accumulation Simulator plots minute-by-minute blood lactate across an entire workout. And the Double Threshold Session Planner generates Norwegian-method AM + PM sessions with rep counts, paces, and estimated lactate levels.
Why Use These Calculators?
- 12 specialized tools covering pace prediction, race strategy, lactate physiology, nutrition, heart rate, and training distribution
- Built on published sports science — VDOT tables (Daniels, 1979), Riegel's power-law formula, Critical Speed regression, Seiler's polarized model, and the Norwegian double-threshold method
- Lactate-focused tools for advanced training: estimate LT1/LT2 thresholds, simulate accumulation curves, and plan Norwegian-style sessions within the 2.3–3.5 mmol/L sweet spot
- Environment-aware pacing: adjust for heat (0.3%/°C), humidity, and altitude with validated correction models
- Race-day fueling plans with per-hour carb targets and gel timing based on event duration and body weight
- Instant results with no sign-up, no payment, no data collection — works on any device in English and Spanish
How to Use Our Running Calculators
- 1
Training paces from a race result
Enter a recent race time into the Training Pace Calculator to get six VDOT-based training zones — from easy recovery to VO₂max intervals. Choose between four prediction models (VDOT, Riegel, Critical Speed, Hybrid) depending on how many race results you have.
- 2
Predict race times across distances
Use the Race Time Predictor to forecast finishing times for seven standard distances (1500m to marathon) with best-case, expected, and conservative estimates. Add the Pace Chart Calculator to generate per-km or per-mile split tables for your target race.
- 3
Map your lactate thresholds and zones
The Lactate Threshold Calculator estimates your LT1 (aerobic) and LT2 (anaerobic) thresholds from a race result, then prescribes five intensity zones. Feed those thresholds into the Lactate Simulator to visualise how blood lactate rises and clears across interval and tempo workouts.
- 4
Plan structured threshold sessions
The Double Threshold Session Planner generates Norwegian-method AM + PM workouts — enter your LT2 pace, target event, fitness level, and weekly volume to get rep counts, interval distances, recovery times, and estimated lactate for each session.
- 5
Audit your training distribution
Log your weekly hours in the Polarized Training Calculator to score your easy/moderate/hard ratio against Seiler's 80/20 framework. See your Polarization Index and get zone-by-zone recommendations.
- 6
Prepare for race-day conditions
The Heat-Adjusted Pace Calculator adjusts your target splits for temperature, humidity, and altitude. Pair it with the Carb Fuel Calculator (per-hour intake and gel timing) and the Sweat Rate Calculator (fluid loss and electrolyte needs) for a complete race-day strategy.
Who Uses These Calculators?
Self-coached runners
Get scientifically prescribed training paces, heart rate zones, and lactate thresholds without hiring a coach. The Training Pace Calculator uses the same VDOT model found in Daniels' Running Formula — the standard text in collegiate coaching.
Marathon and half marathon runners
Predict your race time with confidence ranges, generate per-km split tables, plan carb fueling for distances over 90 minutes, calculate sweat rate from pre/post weigh-ins, and adjust pace targets for heat and altitude.
Threshold-focused athletes
Estimate your LT1 and LT2 from race data, simulate how blood lactate accumulates across a workout, and plan Norwegian-style double threshold sessions designed to keep lactate in the 2.3–3.5 mmol/L training sweet spot.
Runners adopting polarized training
Score your weekly training distribution against the 80/20 model. The Polarized Training Calculator flags when your moderate zone creeps above threshold and recommends zone adjustments.
Running coaches
Generate individualized pace zones, VO₂max estimates, race predictions, and structured threshold sessions for athletes of every level. All tools produce shareable results — no athlete accounts required.
Beginners starting a training plan
Find your easy pace to avoid overtraining, understand your heart rate zones for effort-based running, and learn how much fluid and carbs you need during your first long races.
Hot-climate and altitude runners
The Heat-Adjusted Pace Calculator applies validated correction factors for temperature (0.3%/°C above 10°C), humidity, and altitude (1%/300m above 1500m) so you race with realistic targets.
Sports science students and researchers
Explore the Daniels/Gilbert VDOT model, Riegel's power-law prediction, Critical Speed regression, Seiler's three-zone polarization framework, and the Bakken double-threshold protocol — with real calculations and cited sources.
Under the Hood
The scientific models and engineering decisions behind the 12 calculators.
Four Pace Prediction Models
VDOT Classic (Daniels/Gilbert oxygen cost model, 1979), Riegel (power-law T₂ = T₁ × (D₂/D₁)^1.06), Critical Speed (linear distance-time regression from 2+ races), and Hybrid (60/40 VDOT + CS blend with scaling factor 11.25). Each model uses a different mathematical approach and has different accuracy profiles depending on data availability.
Lactate Kinetics Engine
The Lactate Threshold Calculator estimates LT1 (~2 mmol/L) and LT2 (~4 mmol/L) from race-derived VDOT, mapping to five training zones. The Lactate Simulator models minute-by-minute accumulation using production rate = f(pace/LT2) and clearance rate = f(current_lactate), with configurable interval and recovery segments.
Norwegian Double Threshold Model
Threshold volume = weekly_km × event_ratio × fitness_multiplier, split 55/45 between AM (longer reps at LT2 × 1.03) and PM (shorter reps at LT2 × 0.98). Lactate estimated via 1.5 + 2.5 × (LT2/target)² × (rep_distance/1000). Based on Bakken (2022) and Seiler (2010).
Polarized Training Scoring
Implements Seiler's three-zone model: Zone 1 (below LT1), Zone 2 (LT1–LT2), Zone 3 (above LT2). Calculates a Polarization Index = Z1% + Z3% - Z2% and scores against the 80/20 benchmark. Flags when moderate-zone time exceeds the polarized threshold.
Environment Engine
Three independent correction factors — heat (0.3%/°C above 10°C based on Ely et al., 2007, 1.8M marathon results), humidity (0.1%/pp above 50%), altitude (1%/300m above 1500m) — multiplied together into a single pace multiplier. Classified as Optimal, Moderate, High, or Extreme.
Heart Rate & Nutrition Models
Heart rate zones use the Karvonen formula: Target HR = Resting HR + (HRR × Intensity%). Carb fueling applies the 2.5-hour threshold: 30–60 g/hr for shorter events, 60–90 g/hr for longer. Sweat rate uses the standard body-weight method with validation guards.
Client-Side Architecture
Every calculation runs entirely in your browser using a pure TypeScript math engine with zero framework dependencies. Your race times, body data, and training zones are never sent to any server. No analytics trackers on calculator inputs.