🧱 Construction Tools
Construction Calculators (2026)
Free, accurate construction estimators built for US contractors, DIYers, and homeowners. Calculate concrete volumes, bag counts, home addition costs, stair geometry, and more — no login required.
How to Use These Construction Calculators
Every calculator on this page is designed for real construction scenarios — not just textbook math. Enter your project dimensions, choose your units (feet, inches, or yards), and get an instant material estimate you can take to the hardware store or use to validate a contractor's quote.
For concrete projects: Start with the Concrete Calculator if you need a general estimate, or use the Slab Calculator for flat pours. Always add 10% overage to your order to account for spillage, uneven subgrade, and form waste.
For home additions: The Home Addition Cost Calculator gives itemized estimates by trade (foundation, framing, mechanical, finish work) based on 2026 national average labor and material costs. Use it to budget your project and evaluate contractor bids.
All estimates are starting points. Material costs fluctuate by region and season. Always confirm pricing with local suppliers and get at least three contractor quotes for work over $5,000.
Frequently Asked Questions
How do I calculate how much concrete I need?
Multiply length × width × depth (all in feet) and divide by 27 to get cubic yards. Add 10% for waste. For example, a 10×10 ft patio at 4 inches (0.333 ft) thick = 1.23 cubic yards + 10% = 1.35 cubic yards. Our
Concrete Calculator does this instantly, including bag counts.
How much does a home addition cost per square foot in 2026?
The national average is $80–$200 per square foot depending on region, quality, and type. A basic room addition averages $100/sq ft; a full bathroom addition averages $150–$200/sq ft. High-cost metros like San Francisco or New York can run 1.5–2× the national average.
How many 80 lb bags of concrete do I need for a 10x10 slab?
A 10×10 ft slab at 4 inches thick requires 1.23 cubic yards, or about 55.6 cubic feet. Each 80 lb bag yields approximately 0.60 cubic feet, so you need about 93 bags. Use our
Concrete Bag Calculator to adjust for different thicknesses.
What is the minimum concrete footing depth in Ohio?
Ohio follows IRC frost depth requirements. Most of Ohio requires a minimum footing depth of 36 inches below finished grade (frost depth ranges from 30–42 inches depending on county). Local codes may be more restrictive — always check with your county building department.
What is the maximum stair rise allowed by building code?
Under IRC 2021 (adopted by most US states), the maximum allowable riser height is 8.25 inches and the minimum allowable tread depth is 9 inches. Optimal ergonomic stairs use 7–7.75 inch rise with 10–11 inch tread. Use our
Stair Calculator to compute exact measurements.
