What This Calculator Measures
Estimate runoff reduction using permeable paver area, rainfall, and infiltration rate.
By combining practical inputs into a structured model, this calculator helps you move from vague estimation to clear planning actions you can execute consistently.
This calculator estimates runoff reduction with permeable pavers.
How to Use This Well
- Enter paver area and rainfall.
- Add infiltration rate and drain hours.
- Set runoff coefficient and overflow percent.
- Review runoff reduction.
- Adjust area or drainage.
Formula Breakdown
Runoff = area x rainfall x 0.623 x coeffCapacity: area x rate x hours x 0.623.
Reduction: min(capacity, runoff) / runoff.
Overflow: runoff - capacity.
Worked Example
- 450 sq ft at 1 in rain = 252 gal runoff.
- Capacity about 117 gal.
- Reduction around 46%.
Interpretation Guide
| Range | Meaning | Action |
|---|---|---|
| 70%+ | High. | Great reduction. |
| 40-70% | Good. | Solid impact. |
| 20-40% | Moderate. | Increase area. |
| Below 20% | Low. | Consider upgrades. |
Optimization Playbook
- Increase area: improve reduction.
- Improve base: increase infiltration rate.
- Reduce runoff coeff: use more permeable surfaces.
- Plan overflow: direct overflow safely.
Scenario Planning
- Baseline: current paver area.
- More area: add 100 sq ft.
- Higher rain: add 0.5 in.
- Decision rule: keep reduction above 40%.
Common Mistakes to Avoid
- Ignoring runoff coefficient.
- Overestimating infiltration rate.
- Skipping drain hours.
- Not planning overflow.
Implementation Checklist
- Measure paver area.
- Estimate rainfall events.
- Test infiltration.
- Review reduction.
Measurement Notes
Treat this calculator as a directional planning instrument. Output quality improves when your inputs are anchored to recent real data instead of one-off assumptions.
Run multiple scenarios, document what changed, and keep the decision tied to trends, not a single result snapshot.
FAQ
What is runoff coefficient?
It represents how much rain becomes runoff.
How do I estimate infiltration?
Use soil tests or local guidance.
Should I include overflow?
Yes, overflow planning protects drainage.
Related Calculators
- Rain Garden Runoff Offset Calculator
- Stormwater Cistern Buffer Calculator
- Greywater Reuse Yield Planner Calculator
Frequently Asked Questions
How accurate are the results?
The Permeable Paver Runoff applies a standard formula to your inputs — accuracy depends on how precisely you measure those inputs. For planning and estimation, results are reliable. For high-stakes or professional decisions, cross-check the output with a domain expert or primary source.
How do I account for seasonal variation?
Energy use, carbon emissions, and ecological metrics all vary seasonally. Annual averages are appropriate for long-term planning; monthly or seasonal figures are better for operational decisions like sizing a solar system or planning irrigation. Use your utility bills or metered data for the most accurate baseline.
How should I interpret the Permeable Paver Runoff output?
The result is a calculated estimate based on the formula and your inputs. Compare it against the reference values or benchmarks shown on this page to understand whether your result is high, low, or typical. For decisions with real consequences, use the output as one data point alongside direct measurement and professional advice.
When should I use a different approach?
Use this calculator for quick, formula-based estimates. If your situation involves multiple interacting variables, time-varying inputs, or safety-critical decisions, consider a dedicated software tool, professional consultation, or direct measurement. Calculators are most reliable within their stated assumptions — check that your scenario matches those assumptions before relying on the output.