About OnsiteCalculator
OnsiteCalculator provides free, professional-grade construction calculators and reference charts for contractors, builders, and tradespeople.
Our Mission
We believe every contractor, builder, and homeowner should have access to accurate material calculations without expensive software or complex spreadsheets. Our calculators use industry-standard formulas to help you estimate materials, costs, and project requirements in seconds — right from your phone or laptop.
Why We Built This
After years of seeing contractors struggle with material estimates and homeowners over-order supplies, we created these calculators to solve a real problem. Ordering too much material wastes money. Ordering too little means return trips to the supply yard, wasted fuel, and delays on the job.
Tools like the concrete slab calculator and drywall calculator include waste factors and account for real-world conditions so you can order the right amount the first time. The roofing calculator handles pitch-to-area conversion so you do not have to climb on the roof just to get a ballpark estimate.
What We Offer
Our site includes two types of tools. Material calculators let you enter project dimensions, select materials, and get instant estimates for quantities, bags, and cost. Reference charts provide quick lookup tables for common conversions — like the fraction to decimal chart for tape measure readings and the lumber dimensions chart for nominal vs actual sizes.
Every tool runs entirely in your browser. Nothing is sent to a server, and you do not need to create an account. Results appear instantly and work on any device.
Our Commitment
- All calculators are free to use, no signup required
- Formulas are based on industry standards and real-world material specs
- Regular updates ensure accuracy as material sizes and pricing change
- Mobile-friendly design built for use on job sites, not just desktops
- Printable PDF cheat sheets available for every calculator
Who This Is For
General contractors use our tools for quick takeoffs during bidding. Subcontractors use them to verify material orders before placing them. Homeowners use them to plan DIY projects and check contractor quotes. Whether you are pouring a slab, hanging drywall, or laying flooring, there is a calculator for your job.
Contact Us
Have questions, suggestions, or found an issue with one of our tools? We'd love to hear from you. Reach out and help us make these calculators even better for tradespeople everywhere.