Calculator inputs
Enter storm, field, and drainage values below.
Example data table
Use this sample sports field scenario for quick testing.
| Scenario | Rain rate | Duration | Field size | Runoff % | Drainage + infiltration | Rain depth | Ponding depth | Delay |
|---|---|---|---|---|---|---|---|---|
| Outdoor soccer field | 9.5 mm/h | 2.4 h | 105 m × 68 m | 38% | 7.3 mm/h | 22.80 mm | 3.27 mm | 0h 15m |
| Training pitch | 6.0 mm/h | 1.5 h | 100 m × 64 m | 30% | 6.5 mm/h | 9.00 mm | 1.31 mm | 0h 0m |
Formula used
This calculator estimates how rain affects a sports surface. It combines rainfall, field area, runoff, infiltration, and drainage.
1. Rainfall depth
Rainfall Depth = Rainfall Intensity × Duration
2. Field area
Field Area = Length × Width
3. Potential removal depth
Removal Depth = (Infiltration Rate + Drainage Rate) × Duration
4. Effective water depth
Effective Depth = Rainfall Depth − Removed Depth
5. Runoff depth
Runoff Depth = Effective Depth × Runoff Coefficient
6. Surface ponding depth
Ponding Depth = Effective Depth − Runoff Depth
7. Water volume
Volume = Field Area × Depth ÷ 1000
8. Delay estimate
Delay = (Ponding Depth − Playable Threshold) ÷ Combined Removal Rate
All depth values are converted to millimeters internally. Field dimensions are converted to meters before volume calculations begin.
How to use this calculator
- Enter rainfall intensity and storm duration.
- Select your rainfall unit.
- Enter field length and width.
- Choose meters or feet for field dimensions.
- Add runoff, infiltration, and drainage estimates.
- Set the maximum water depth allowed for play.
- Press the calculate button.
- Review the result cards, graph, and export options.
Frequently asked questions
1. What does this rainfall calculator measure?
It estimates rain depth, total water volume, runoff, ponding depth, drying time, and likely delay for a sports field after a storm event.
2. Why is runoff coefficient important?
Runoff coefficient shows how much effective water leaves the surface instead of remaining on it. Higher values usually reduce ponding depth.
3. What is a playable threshold?
It is the maximum standing water depth you consider acceptable for training or match use. Lower thresholds create more conservative delay estimates.
4. Can I use feet and inches?
Yes. The calculator accepts feet for field size and inches per hour for rain-related rates, then converts everything internally.
5. Does this replace a field inspection?
No. It provides an estimate only. Actual playability also depends on turf condition, slope, soil compaction, maintenance quality, and safety rules.
6. What happens if drainage rate is zero?
The calculator will rely only on infiltration to reduce ponding. If both drainage and infiltration are zero, drying time becomes unavailable.
7. Can this help with scheduling?
Yes. Coaches, facility managers, and grounds teams can use it to compare storm scenarios before practice, matches, or surface maintenance.
8. What does the graph show?
The graph tracks cumulative rainfall and surface ponding over time. It also shows the playable threshold for quick visual comparison.