Calculator Inputs
Use steady-state running data for the cleanest result. The field grid is three columns on large screens, two on medium screens, and one on mobile.
Plotly Graph
The chart compares your estimated oxygen demand curve with the ACSM reference curve at the same grade.
Formula Used
- Speed (km/h) = Distance ÷ Time × 60
- Speed (m/min) = Distance × 1000 ÷ Time
- Pace (min/km) = Time ÷ Distance
- Oxygen Cost (ml/kg/km) = Measured VO₂ × 60 ÷ Speed (km/h)
- Absolute VO₂ (ml/min) = Adjusted VO₂ × Body Mass
- Energy (kcal/min) = Absolute VO₂ (L/min) × 5
- ACSM Running VO₂ = 0.2 × Speed(m/min) + 0.9 × Speed(m/min) × Grade + 3.5
- Temperature Factor = 1 + max(0, |Temp − 12| − 5) × 0.005
- Wind Factor = 1 + Headwind × 0.003
- Adjusted VO₂ = Measured VO₂ × Surface Factor × Temperature Factor × Wind Factor
- Economy Index = ACSM VO₂ ÷ Adjusted VO₂ × 100
- O₂ per Step = Absolute VO₂ (ml/min) ÷ Cadence
Lower oxygen cost per kilometer usually reflects better running economy. The economy index compares your corrected demand to a reference demand at the same speed and grade.
How to Use This Calculator
- Enter a steady run distance and total session time.
- Add body mass and measured or estimated VO₂.
- Include cadence, heart rate, grade, and any headwind resistance.
- Select the running surface that best matches the session.
- Choose a projection distance for future pacing and calorie estimates.
- Press the calculate button to show results above the form.
- Review oxygen cost, energy demand, step metrics, and economy index.
- Use the CSV or PDF buttons to save the result set.
Example Data Table
| Session | Distance (km) | Time (min) | VO₂ (ml/kg/min) | Speed (km/h) | Oxygen Cost (ml/kg/km) | Economy Index |
|---|---|---|---|---|---|---|
| Easy Aerobic | 8.0 | 44.0 | 40.0 | 10.91 | 220.00 | 99.7 |
| Tempo Session | 6.0 | 25.0 | 44.5 | 14.40 | 185.42 | 104.0 |
| Threshold Run | 5.0 | 21.0 | 48.0 | 14.29 | 201.60 | 99.2 |
FAQs
1. What is running economy?
Running economy describes how much oxygen you need to maintain a given running speed. Lower oxygen demand at the same pace usually means more efficient running.
2. Why is oxygen cost shown per kilometer?
Cost per kilometer makes different runs easier to compare. It converts momentary oxygen demand into a distance-based efficiency value that coaches often review.
3. Is a lower oxygen cost always better?
Usually yes. Lower oxygen cost suggests the runner is spending less energy to cover the same distance, though terrain, fatigue, heat, and wind can still change the picture.
4. Why does the calculator use cadence?
Cadence helps estimate step length and oxygen cost per step. Those values can reveal whether economy changes are coming from stride mechanics or pacing choices.
5. What does the economy index mean?
The economy index compares your corrected oxygen demand with a reference demand. Values above 100 suggest better-than-reference economy for that speed and grade.
6. Should I use treadmill or outdoor data?
Either can work. Just match the surface selection to the session and keep the testing conditions consistent when you compare runs over time.
7. Are temperature and wind corrections exact?
No. They are light planning adjustments, not lab-grade corrections. They help normalize sessions when weather clearly changed effort demands.
8. When should I trust the results most?
Use steady runs, reliable VO₂ estimates, and realistic environmental inputs. Repeat the same protocol over multiple sessions to spot meaningful trends.