roof calculator square feet
Statistical cost estimator for roof drainage / pipe systems – confidence‑based, inflation‑ready, globally adaptable.
📐 input parameters & project conditions
Fill in the fields below. All numbers are validated; negative values are not allowed. The sample dataset drives the statistics — use at least 3 values.
📊 statistical cost output
Results based on your sample and adjusted for multipliers, depth, soil, permit, and inflation.
adjusted mean cost
$ —
lower bound (CI)
$ —
upper bound (CI)
$ —
cost per ft
$ —
inflation‑adj. mean
$ —
| statistical metric | value | explanation |
|---|---|---|
| sample size (n) | — | number of project samples |
| mean (raw sample) | — | average of raw sample |
| standard deviation | — | sample std deviation |
| margin of error | — | z · (σ/√n) |
| z‑score used | — | based on confidence level |
📈 cost distribution histogram (sample)
Visual distribution of your raw sample data.
🔍 factor impact tables
soil condition cost factors
| soil type | factor | impact on total cost |
|---|---|---|
| normal | 1.0 | baseline |
| rocky | 1.3 | +30% (blasting/break) |
| clay | 1.1 | +10% (sticky, dewater) |
| sand | 0.9 | -10% (easy digging) |
confidence level comparison (on raw sample)
| confidence | z‑score | interval width |
|---|---|---|
| 90% | 1.645 | — |
| 95% | 1.96 | — |
| 99% | 2.576 | — |
final result interpretation
| component | amount | description |
|---|---|---|
| raw sample mean | — | before multipliers |
| conditions multiplier | — | soil, depth, material, regional, labor/mat multipliers |
| added permit | $500 | fixed permit cost |
| inflation factor | — | (1+inf)^(current-model) |
| final adjusted mean | — | after all adjustments |
❓ frequently asked questions
- How is trench depth factor calculated? Base depth = 3 ft. For every extra foot, cost increases 5%: factor = 1 + max(0, depth-3)*0.05.
- Does the calculator work for any currency? Yes, enter numbers in your currency — all outputs use same unit.
- What if my sample has fewer than 2 values? Statistics require at least 2; we’ll show an error.
- Why is there a regional modifier? To adjust for labour/material cost differences between cities/countries.
Use the Cost to Run Water Line 1000 Feet Calculator to estimate your water line cost, or explore the full Feet & Inches Measurement Calculator category for all length and measurement tools.