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RunCalcs Help

Understanding the science behind your calculations.

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Race Pace Calculator

The Race Pace Calculator determines your target pace per kilometer or mile based on your desired race distance and target completion time.

Primary Formula:
Pace = Total Time ÷ Distance
This fundamental calculation converts your total race time into a per-unit pace, helping you maintain consistent speed throughout your race.
Speed Calculation:
Speed = Distance ÷ Total Time (in hours)
Distance: Race distance in km or miles
Time: Target completion time (hours:minutes:seconds)
Usage Tips:
  • Start conservatively - aim for negative splits (faster second half)
  • Practice your target pace during training runs
  • Account for course elevation and weather conditions
  • Use during tempo runs and race simulation workouts
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Race Time Predictor

The Race Time Predictor uses the scientifically validated Riegel Formula to estimate your performance at different race distances based on a known race result.

Riegel Formula:
T2 = T1 × (D2 ÷ D1)^1.06
T2: Predicted time for target distance
T1: Known time from previous race
D2: Target race distance
D1: Known race distance
1.06: Fatigue factor (accounts for physiological limitations at longer distances)
The exponent 1.06 represents the fatigue factor, acknowledging that performance doesn't scale linearly with distance due to physiological limitations and pacing strategies.
Accuracy Notes:
Most accurate for distances between 1500m and marathon. Results may vary ±5-10% based on individual training background, course conditions, and race strategy. Best used with recent race times (within 3-6 months).
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Splits Calculator

The Splits Calculator creates even pacing plans by dividing your goal time by distance and chosen split interval.

Lap Time Formula:
Lap Time = (Total Time ÷ Distance) × Interval
Distance: Total race distance
Interval: Split distance (e.g., 1 km)
Total Time: Target finish time
Usage Tips:
  • Match the interval to course markers or track laps
  • Download the generated table for race planning
  • Supports both metric and imperial units
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VO2 Max Calculator

Our VO2 Max Calculator uses the official Jack Daniels and Gilbert VDOT formula, which is considered the gold standard for estimating VO2 Max from race performance data.

Jack Daniels VDOT Formula:
VO2 Max = (-4.60 + 0.182258 × S + 0.000104 × S²) ÷ (0.8 + 0.1894393 × e^(-0.012778 × T) + 0.2989558 × e^(-0.1932605 × T))
S: Speed in meters per minute
T: Time in minutes
e: Mathematical constant (≈2.718)
Additional Calculations:
Running Economy = (VO2 Max ÷ Speed in km/h) × 60
vVO2max ≈ Current Speed × 1.05
Running economy represents oxygen cost per kilometer, while vVO2max estimates the velocity at which you reach maximum oxygen uptake.
Scientific Validation:
The VDOT system has been validated against laboratory VO2 Max testing with correlation coefficients above 0.90. Most accurate with race distances from 1500m to marathon, performed at maximum effort within the last 6 months.
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Heart Rate Zone Calculator

Heart rate zones are calculated using either the Maximum Heart Rate method or the more accurate Karvonen (Heart Rate Reserve) method when resting heart rate is provided.

Maximum Heart Rate (Tanaka Formula):
Max HR = 208 - (0.7 × Age)
The Tanaka formula is more accurate than the traditional "220 - Age" formula, especially for older adults and trained athletes.
Karvonen Method (Heart Rate Reserve):
Target HR = ((Max HR - Resting HR) × Intensity %) + Resting HR
Zone 1: 50-60% - Active Recovery
Zone 2: 60-70% - Base Training
Zone 3: 70-80% - Aerobic
Zone 4: 80-90% - Lactate Threshold
Zone 5: 90-100% - VO2 Max
Training Zone Guidelines:
  • Spend 80% of training time in Zones 1-2 (aerobic base)
  • Use Zone 4 for tempo runs and lactate threshold training
  • Zone 5 intervals should be limited to 1-2 sessions per week
  • Consider getting a lactate threshold test for more precise zones
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Recovery Time Calculator

Recovery time estimation is based on exercise physiology research correlating training intensity, duration, and physiological stress markers with optimal recovery periods.

Heart Rate Reserve Intensity:
Intensity % = ((Exercise HR - Resting HR) ÷ (Max HR - Resting HR)) × 100
This calculation determines training intensity based on heart rate reserve, which is then mapped to recovery requirements.
Recovery Time Calculation:
Base Recovery = Exercise Duration × Intensity Factor × Duration Multiplier
Intensity Factors: Very Light: 0.5x, Light: 1.0x, Moderate: 1.5x, Hard: 2.5x, Very Hard: 4.0x
Duration Multiplier: 1.0x (≤60min), 1.1x (60-120min), 1.3x (>120min)
Individual Variation:
Recovery times are estimates based on population averages. Individual factors including age, fitness level, nutrition, sleep quality, stress levels, and training history can significantly affect actual recovery needs. Always listen to your body and adjust accordingly.
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BMI Calculator

Body Mass Index (BMI) is a simple screening tool that uses height and weight to categorize weight status. While widely used, it has limitations for athletes and individuals with high muscle mass.

BMI Formula:
BMI = Weight (kg) ÷ Height (m)²
For imperial units: BMI = (Weight in pounds × 703) ÷ (Height in inches)²
BMI Categories:
< 18.5: Underweight
18.5-24.9: Normal weight
25.0-29.9: Overweight
≥ 30.0: Obese
Healthy Weight Range:
Minimum Healthy Weight = 18.5 × Height (m)²
Maximum Healthy Weight = 24.9 × Height (m)²
BMI Limitations:
BMI doesn't distinguish between muscle and fat mass, may not be accurate for athletes, older adults, or certain ethnic groups. It's a screening tool, not a diagnostic measure. Consider body composition analysis and consult healthcare professionals for comprehensive health assessment.