Run the numbers before you send the bid. Every calculator works in the browser with no sign-up.
Markup vs margin calculator — Markup is profit as a percentage of your cost; margin is profit as a percentage of your price. They are never the same number. To convert markup to margin: margin = markup / (1 + markup). To price for a target margin: price = cost / (1 - margin). A 50% markup produces only a 33.3% margin, which is why pricing off markup quietly underprices most contractors.
Labor burden calculator — Labor burden is everything an employee costs you beyond their base wage: payroll taxes, workers compensation, liability insurance, benefits, paid time off and vehicle or tool allowances. Your burdened rate = (annual wages + all burden costs) / actual billable hours worked. Because burden commonly adds 25% to 40% on top of the wage, and unbillable hours shrink the divisor, a $25/hour employee often costs $38 to $45 per billable hour.
Contractor hourly rate calculator — Your minimum hourly rate = (annual overhead + target owner pay + desired profit + direct labor cost) / billable hours per year. Most contractors set rates by copying competitors, which only works if their overhead and billable-hour count match yours. Work the number from your own costs first, then check it against the market.
Job profit calculator — Job profit = contract price + approved change orders - materials - labor - subcontractors - equipment - overhead allocation. The number most contractors track is gross profit, which ignores overhead and therefore overstates how well the job did. Allocating overhead as a percentage of revenue turns gross profit into the net figure that actually reaches your bank account.
Retainage calculator — Retainage (also called retention) is a percentage of each progress payment the owner withholds until the job is complete, typically 5% to 10%. Retainage withheld per draw = draw amount x retainage %. On a $200,000 contract at 10% retainage, $20,000 is held back across the draws and released at completion, which is often the contractor's entire profit sitting in someone else's account.
Square footage calculator — Square footage = length (ft) x width (ft). For material ordering, add a waste factor: order quantity = square footage x (1 + waste %). Typical waste allowances run about 5% to 10% for straightforward rectangular layouts and 10% to 15% for diagonal patterns, complex rooms or material with a repeating pattern that has to be matched.
Concrete calculator — Concrete volume in cubic yards = (length ft x width ft x thickness in inches / 12) / 27. A 4-inch slab covers roughly 81 square feet per cubic yard. Always add a waste allowance, commonly 5% to 10%, for subgrade variation, spillage and over-excavation, since running short mid-pour is far more expensive than ordering slightly over.
Roofing squares calculator — One roofing square equals 100 square feet of roof surface. Roof area = footprint area x pitch multiplier, then squares = roof area / 100. A 6/12 pitch has a multiplier of about 1.118, so a 2,000 sq ft footprint is roughly 2,236 sq ft of roof, or 22.4 squares before waste. Architectural shingles are typically sold three bundles per square.
Paint coverage calculator — Paintable wall area = perimeter x ceiling height, minus doors and windows. Gallons needed = (area x number of coats) / coverage per gallon. One gallon typically covers 350 to 400 square feet per coat on smooth, previously painted surfaces, and noticeably less on textured, porous or unprimed substrates.
Material waste factor calculator — Order quantity = takeoff quantity x (1 + waste %). Waste factors exist because materials are cut, damaged, mismeasured and sold in fixed package sizes. Typical allowances run about 5% to 10% for simple rectangular layouts and 10% to 15% or more for complex, patterned or heavily cut-up work. Under-ordering usually costs more than over-ordering once a return trip, delayed crew and batch mismatch are priced in.