EngineeringFormulaCivil & Structural
Civil and structural calculations
Beam checks, section properties, concrete volume, rebar weight, decking, retaining walls, roofing, and construction material takeoffs.
Engineering Guides
A practical starting point for engineering calculations: choose the right calculator, understand the equation behind it, check assumptions, and follow solved examples when the calculation needs more context than a single input form can show.
Last meaningfully updated September 7, 2026.
Start with the right engineering guide
How to choose the right calculator
Start with the quantity you need, then match the formula family: force and motion, electrical power, heat transfer, fluid flow, or structural sizing.
Browse calculator index →How to read an engineering formula
Identify the target variable, convert units before substitution, check assumptions, and compare the result against a practical range.
Open formula index →How to solve common calculation problems
Walk through popular problems step by step, including concrete volume, voltage drop, beam deflection, wire size, Ohm's law, and force.
View solved examples →How to avoid unit mistakes
Use consistent units, distinguish absolute and relative temperature, and check whether the calculator reports SI, US customary, or trade units.
Open unit conversions →Popular workflows
Start with the problem users actually search for
Concrete quantity and material takeoff
Start with concrete volume, then branch into rebar weight, footing size, slab quantity, and mix-ratio checks before ordering material.
Follow concrete calculation steps →Wire, breaker, and voltage-drop sizing
Estimate current, choose a breaker for continuous load, size the wire, then verify voltage drop on the actual run length.
Follow electrical sizing steps →HVAC airflow and load checks
Use HVAC load, BTU, CFM, duct size, static pressure, and air changes per hour together instead of treating them as isolated numbers.
Follow HVAC calculation steps →Browse by discipline
Calculation guides by engineering area
25 tools
Engineering Mechanics
Engineering mechanics calculations
Newton's second law, net force, acceleration, velocity, energy, momentum, free fall, projectile motion, and impact force problems.
Mechanical
Mechanical design calculations
Torque, shaft sizing, belt speed, gear ratio, pulley ratio, horsepower, stress, strain, and weld or bolt checks.
Electrical
Electrical calculations
Ohm's law, voltage drop, wire gauge, breaker sizing, LED resistors, power factor, kWh, batteries, capacitors, and resistor codes.
Fluid Mechanics
Fluid mechanics calculations
Flow rate, pipe size, Reynolds number, Bernoulli equation, hydrostatic pressure, buoyancy, pump power, ducts, and CFM.
Thermodynamics
Thermodynamics and HVAC calculations
Heat energy, conduction, convection, heat loss, U-value, BTU sizing, HVAC load, ideal gas law, Carnot efficiency, dew point, and wind chill.
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New calculator guides now connected from this hub
Method
A good calculation is more than a formula
EngineeringFormula guides are organized around the way real users get unstuck: first identify the formula, then convert units, then substitute values, then decide whether the result is usable inside the stated assumptions. That last step matters most, because a mathematically correct answer can still be the wrong design answer if the model does not match the situation.
Start from the required output, not from the equation name.
Convert mixed units before comparing or multiplying values.
Check whether the calculator uses average, peak, nominal, or design values.
Read the assumptions before using a result for buying, sizing, or safety decisions.
Common guide questions
Should I use a calculator, formula, or solved example?
Use a calculator when you already know the inputs and need a result. Use the formula index when you are checking variables or units. Use solved examples when you want to see the substitution steps before doing your own calculation.
Are these guides a replacement for engineering design review?
No. They are educational and planning references. Structural, electrical, HVAC, and safety-critical work still needs the applicable code, manufacturer data, and a qualified professional where required.
Why are assumptions shown so prominently?
A formula is only valid inside its assumptions. The same number can be useful or misleading depending on support conditions, units, material properties, temperature range, flow regime, or local code requirements.