Free construction and engineering calculators
Quick estimates with the formula shown and a worked example. Use them to plan and budget. Anything structural, retaining or drainage on a permitted project still needs a sealed design.
Building
Concrete
Concrete Bag CalculatorFind how many 40, 60 or 80 lb bags of premixed concrete you need for a small slab, pad or footing.Concrete Cylinder Strength and Water-Cement Ratio CalculatorCompute compressive strength from a cylinder break load and diameter, and the water-cement ratio of a mix by weight.Concrete Slab CalculatorCalculate cubic yards of concrete for a slab, patio or driveway, including a waste allowance and an order quantity rounded to the quarter yard.Concrete Slab Cost CalculatorEstimate the cost of a concrete slab from its size, your local ready-mix price per yard and an installed labor rate per square foot.Continuous Footing Concrete CalculatorEstimate concrete for a continuous wall footing (strip footing) from its total length, width and depth.Rebar Grid CalculatorEstimate the number of bars, total length and weight of rebar for a slab grid at a given spacing, with lap and waste allowance.Round Column and Sonotube CalculatorCalculate concrete volume for round columns, piers and sonotube forms, with total cubic yards and 80 lb bag count.
Earthwork
Cut and Fill Volume Calculator (Average End Area)Compute earthwork volume between two cross-sections using the average end area method, in cubic feet and cubic yards.Earthwork Swell and Shrink CalculatorConvert earthwork between bank, loose and compacted cubic yards using swell and shrinkage factors, and find borrow needed for fill.Excavation Volume CalculatorCalculate bank and loose cubic yards of excavation for a basement or pit, plus the number of truckloads to haul it.Trench Volume CalculatorCalculate trench excavation, pipe displacement and backfill volume in cubic yards for utility and drain pipe trenches.
Geotechnical
Hydraulics and pipes
Culvert Capacity Calculator (Screening)Screen a round culvert's capacity using the submerged inlet orifice equation and Manning's full-barrel flow; the lower value governs.Hazen-Williams Head Loss CalculatorCalculate friction head loss and pressure drop in water pipes with the Hazen-Williams equation from flow, diameter, length and C factor.Manning's Equation Pipe Flow CalculatorCalculate full-flow capacity and velocity of a circular pipe with Manning's equation from diameter, slope and roughness n.Pipe Slope CalculatorCalculate pipe slope in ft/ft, percent and inches per foot from upstream and downstream invert elevations and pipe length.
Masonry
Materials
Asphalt Tonnage CalculatorCalculate tons of hot mix asphalt for a driveway or parking lot from area, compacted thickness and mix density.Gravel CalculatorCalculate cubic yards and tons of gravel or crushed stone for a driveway, path or base course.Mulch CalculatorCalculate cubic yards of mulch and the number of 2 and 3 cubic foot bags for a bed area and depth.Topsoil CalculatorCalculate cubic yards of topsoil for lawns and garden beds from area and depth.
Roads and transportation
Horizontal Curve CalculatorCompute circular horizontal curve elements: tangent length, curve length, long chord, external, middle ordinate and degree of curve.Pavement Structural Number Calculator (AASHTO 93)Calculate the AASHTO 1993 structural number SN of a flexible pavement from layer thicknesses, layer coefficients and drainage coefficients.Stopping Sight Distance CalculatorCalculate AASHTO stopping sight distance from design speed, perception-reaction time, deceleration rate and grade.Vertical Curve CalculatorCalculate elevations on a parabolic vertical curve, the high or low point and the K value from grades, length and PVC elevation.
Septic and wastewater
Site work
Stormwater
Detention Pond Volume Calculator (Modified Rational)Estimate required stormwater detention storage with the modified rational method from inflow, storm duration and allowable release rate.NRCS Curve Number Runoff CalculatorCalculate direct runoff depth and volume from rainfall and NRCS (SCS) curve number using the TR-55 runoff equation.Rainfall Intensity CalculatorConvert a rainfall depth over a storm duration into average intensity in inches per hour and millimeters per hour.Rational Method Runoff Calculator (Q = CiA)Estimate peak stormwater runoff in cfs with the rational method Q = CiA from runoff coefficient, rainfall intensity and drainage area.Roof Runoff and Rainwater Harvesting CalculatorCalculate gallons of runoff from a roof or paved area for a given rainfall depth, for rain barrels, cisterns and drywells.Time of Concentration Calculator (Kirpich)Estimate a watershed's time of concentration in minutes with the Kirpich formula from flow length and average slope.
Structural
ASCE 7 LRFD Load Combination CalculatorApply the ASCE 7 strength design (LRFD) load combinations to dead, live, roof live, snow and wind loads and find the governing value.Column Buckling Calculator (Euler and AISC)Calculate the Euler critical buckling load of a column and the AISC 360 flexural buckling design strength for steel members.Flat Roof Snow Load Calculator (ASCE 7)Calculate the ASCE 7 flat roof snow load pf = 0.7·Ce·Ct·Is·pg and the minimum roof snow load from ground snow load.Point Load on Beam CalculatorFind support reactions, maximum moment and deflection under a single point load anywhere on a simply supported beam.Rectangular Section Properties CalculatorCompute area, moment of inertia, section modulus and radius of gyration of a rectangular section such as a wood joist or beam.Simple Beam Deflection Calculator (Uniform Load)Calculate maximum moment, shear, bending stress and midspan deflection for a simply supported beam under a uniform load.Wind Velocity Pressure Calculator (ASCE 7)Calculate ASCE 7 velocity pressure qz from basic wind speed and exposure factors, with a simple windward wall pressure estimate.
Unit conversions
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