Construction & DIY
Calculators.

Materials, electrical, roofing, and landscaping — build with confidence, not guesswork.
92 Tools
17 Subcategories
Always Free

Material takeoffs, HVAC sizing, electrical loads, structural spans, and the guide that ties them together. Plan the project, order the right quantity, and budget the labor — before you swing a hammer or pull a permit.

Use this hub when:
  • You're estimating materials for a project and want a defensible number, not a guess.
  • You're sizing HVAC, electrical, or plumbing and need the engineering-style math.
  • You're budgeting a renovation and want a plan that sequences the decisions.

Pick by what you're deciding

The same pages, grouped by the question you're trying to answer.

Plumbing, water heaters & pool

Pipe sizing, fixture-unit loads, septic capacity, and the chemistry that keeps water swimmable.

Framing & structural loads

Stud counts, joist spans, beam sizing, and the wind-load math under the cosmetic finishes.

Pick a path based on your project

Material estimates, permit checks, and load math grouped by project type.

Electrical

14 tools

Wire sizing, resistor values, and circuit calculations — get the math right before you wire.

Wire Size Calculator

NEC-compliant wire gauge for safe, efficient circuits.

gaugeampacity

Ohm's Law

Voltage, current, resistance, and power relationships.

circuitpower

Voltage Divider

Output voltage from two resistors in series.

resistorsignal

LED Resistor

Current-limiting resistor for single and series LEDs.

LEDcurrent

Resistor Color Code

4, 5, and 6-band resistor color code decoder.

color codebands

Electricity Cost

Monthly and annual energy cost from watts and hours.

costkWh

Generator Sizing

Calculate backup generator size from your appliance list.

generatorwatts

Circuit Breaker Size

NEC-compliant breaker sizing with GFCI/AFCI requirements.

breakerNEC

Conduit Fill

Check NEC wire fill percentage for EMT, PVC, and Rigid conduit.

conduitfill%

Solar Panel Size

How many panels you need, battery sizing, and 25-year ROI.

solarPV

EV Charger Sizing

Breaker size, wire gauge, panel load & charging time per NEC 625.

NEC 625Level 2

Electrical Panel Load

NEC 220 demand load calculation — service size and capacity analysis.

NEC 220demand factor

Ground Fault (GFCI) Calculator

NEC 2020 GFCI and AFCI requirements by room type — outlet count, code sections, and protection cost estimates.

GFCIAFCINEC 2020

Lighting Layout Calculator

Foot-candle targets, fixture count, and grid spacing by room type — zonal cavity method with efficacy and energy density checks.

foot-candlesfixture countzonal cavity

Structural & Framing

8 tools

Size beams, frame walls, calculate lumber quantities — professional structural calculations without the engineering fees.

Frequently asked questions

How accurate are these material takeoffs?

Each calculator uses the same waste-factor and overage rules a job-site estimator would apply. The defaults err on the side of slightly over-ordering (because under-ordering costs more in delivery fees and lost time than the extra material). You can adjust the waste factor on every quantity calculator.

Are the engineering calculators (HVAC, structural, electrical) code-compliant?

They use ASHRAE Manual J/D/S (HVAC), NEC current edition (electrical), and IBC/IRC current editions (structural) as the basis. They produce defensible numbers for planning and permit submission, but any project that requires a stamped drawing should be reviewed by a licensed engineer in your jurisdiction.

What's the difference between the Material Estimation guide and the calculators?

The guide explains the unit-of-measure conventions (cubic yards vs bags, board-feet vs linear-feet, squares vs square-feet) and the waste-factor framework. The calculators apply those conventions to your specific dimensions. Read the guide once; bookmark the calculators.

Do these calculators handle metric units?

Most have a unit-toggle in the input panel that switches between US customary (inches, feet, pounds, °F) and metric (cm, m, kg, °C). The structural and electrical calculators expose the underlying conversion factors so you can verify the math.

Why isn't there a permit-cost calculator for my city?

The Permit Fee Calculator handles the most common jurisdictional fee schedules (IBC valuation method, plan-review percentage, plumbing fixture unit fee). For city-specific fees, link your jurisdiction's permit office page from inside the calculator — the inputs are flexible enough to model most local schedules.

Explore More

Environment Calculators → Daily Life Calculators → Material Estimating Guide →