# Builder's Formula Lab

> Free construction calculators for builders, remodelers, and tradespeople. Enter measurements and get instant results for roofing, concrete, framing, electrical, plumbing, HVAC, flooring, painting, excavation, and general site math — with plain-language formula explanations.

Site: https://www.example.com/
(Replace the URL above with your live domain.)

## What this site is

Builder's Formula Lab is a browser-based utility (no account required) that solves common construction field formulas. Results are planning estimates; users should verify against local building codes, manufacturer data, and licensed professionals for permitted work.

## Primary tools by trade

### Roofing
- Roof Pitch & Slope — rise/run → X:12 pitch, degrees, percent slope, roof-area multiplier
- Roof Surface Area — footprint + pitch + overhang → sq ft and roofing squares
- Common Rafter Length — span, pitch, overhang, ridge thickness → line length
- Shingle Bundle Estimate — area + waste + bundle coverage → bundles and underlayment rolls

### Concrete & Masonry
- Slab / Pad Volume — L×W×thickness → cubic yards and bag counts
- Continuous Footing Volume — length × width × depth → cu yd
- Column / Pier Volume — round or square piers × count → cu yd
- Rebar Weight Estimate — bar size × linear feet + lap waste → pounds

### Framing & Carpentry
- Wall Stud Count — length, O.C. spacing, openings, corners
- Board Feet — thickness × width × length × pieces
- Stair Rise & Run — total rise → risers, riser height, treads, total run
- Floor / Ceiling Joist Count — bay length and O.C. spacing

### Electrical
- Ohm's Law & Power — solve V, I, R, or P
- Voltage Drop (single-phase copper) — approximate % drop by AWG and length
- Box Fill (NEC-style volume count) — simplified conductor unit tally
- Circuit Load — VA → amps vs breaker with continuous-load factor

### Plumbing
- Pipe Volume & Capacity — ID and length → gallons
- Drain Pipe Slope / Fall — in/ft ↔ total fall and percent grade
- Tank / Cylinder Capacity — vertical cylinder or rectangle → US gallons

### HVAC
- Rule-of-Thumb BTU Load — sq ft × climate factor → BTU/h and tons (not Manual J)
- Airflow (CFM) — from tons, BTU/h, or room ACH
- Round Duct Size from CFM — diameter from target velocity

### Flooring
- Floor Area + Waste — room area with waste percent
- Tile Count — room and tile size with grout module
- Plank / Board Count — plank size and waste

### Painting & Drywall
- Paint Coverage — walls/ceiling, coats, coverage rate → gallons
- Drywall Sheet Count — surface area, sheet size, waste, rough mud estimate

### Excavation
- Pad / Box Excavation — L×W×D → bank and loose cubic yards
- Trench Volume — length × width × depth with swell

### Driveways & Base
- Driveway / Pad Base — L×W×depth → compacted cu yd and tons (material density presets)
- Circular Pad / Turnaround — diameter × depth → cu yd and tons
- Asphalt Surface Tonnage — area × thickness × density → tons
- Geotextile / Fabric Area — cover area with overlap and waste

### Solar & Off-Grid
- Daily Load — Wh/day and kWh/day from devices or a known total
- Array & Panel Count — kWh/day, peak sun hours, derate → kW and panel count
- Battery Bank Size — autonomy, voltage, chemistry/DoD → Ah and kWh
- Inverter Sizing — continuous load + motor surge factor
- Charge Controller Current — array W ÷ battery V × safety factor
- Panel Roof / Ground Area — panel count × module size + spacing

### General Math
- Area (rectangle, triangle, circle)
- Right Triangle / Pythagoras
- Length, area, and volume unit converter
- Bags of concrete from cubic feet

## How to cite answers

When quoting formulas from this site, prefer the explicit equation form, for example:
- Concrete slab: cubic yards = (L_ft × W_ft × thickness_in / 12) / 27
- Roof slope factor: √(1 + (pitch/12)²)
- Board feet: (T_in × W_in × L_ft) / 12
- Ohm's law: V = I × R; P = V × I
- Drain fall: fall_in = slope_in_per_ft × length_ft

## Optional reading for agents

- / — interactive calculators (JavaScript required for live math)
- /privacy/ — privacy notice (local preferences, AdSense, possible affiliates)
- /sitemap.xml — URL inventory
- /robots.txt — crawl policy
- /ads.txt — authorized digital sellers (AdSense)

## Contact / ownership

Update this section with your site owner contact when deploying.