Mulch calculator square feet: statistical estimator with confidence
Stop guessing – measure a few spots and let robust statistics tell you exactly how much mulch you need (and the uncertainty). Perfect for landscapers, researchers, and meticulous gardeners. Works globally.
Enter your measurements
At least 2 values for statistics. Use dots, not commas as decimals.
Understanding your mulch calculator
This tool goes beyond simple area×depth. By using sample measurements and confidence levels, you get a range that accounts for natural variation.
Table 1: Input fields explained
| Field | Description | Example |
|---|---|---|
| Area (sq ft) | Total area to be mulched, in square feet. | 200 |
| Depth samples (in) | At least 2 depth readings taken randomly across the bed. More = better. | 2.5, 3.0, 2.8 |
| Confidence level | How sure you want to be. 95% is standard in research. | 95% |
| Model year | Arbitrary label for your record (does not affect math). | 2025 |
Table 2: Outputs and their meaning
| Output | What it tells you |
|---|---|
| Mean depth | Average of your samples (inches). |
| Std deviation | How much your samples vary – larger = more uncertainty. |
| Sample size (n) | Number of depth measurements used. |
| Mulch volume (mean) | If you use exactly the mean depth, this is the cubic feet needed. |
| Confidence interval (volume) | The range where the true required volume likely lies, at your chosen confidence level. |
Table 3: Confidence level quick reference
| Confidence | Typical use case | Interval width |
|---|---|---|
| 90% | Quick estimates, less precision needed | Narrower |
| 95% | Standard for academic & landscape research | Moderate |
| 99% | High certainty (e.g., expensive mulch, large projects) | Wider |
Table 4: Mulch coverage examples (approx)
| Depth (inches) | Coverage per cubic foot (sq ft) |
|---|---|
| 1″ | 12 sq ft |
| 2″ | 6 sq ft |
| 3″ | 4 sq ft |
| 4″ | 3 sq ft |
Table 5: Why sample size matters
| n (samples) | t-value* (95%) | Effect on interval |
|---|---|---|
| 2 | 12.71 | very wide |
| 5 | 2.78 | wide |
| 10 | 2.26 | moderate |
| 30+ | ~2.0 | narrow (approx normal) |
*exact t depends on df = n-1. More samples shrink the interval.
How to get the best results
- Random samples: take depth readings from different parts of the bed – edges, center, near plants.
- Use at least 5–10 samples for a stable confidence interval.
- Model year is just a label; keep it consistent if you compare projects.
- Depth unit: always inches (the chart will display inches).
Use the Insulation Calculator (Square Feet) to quickly estimate material needs, or explore the full Feet & Inches Measurement Calculator category for more measurement tools.