Engineering Calculators
Unit conversion, electrical, civil & more.
What Are Engineering Calculators?
Engineering calculators provide precise computations for the problems that arise across electrical, civil, mechanical, and structural engineering disciplines. Whether you are sizing a cable for a domestic electrical installation, calculating the deflection of a beam under load, converting between international unit systems, or working out the concrete volume needed for a foundation, these tools deliver reliable answers grounded in established engineering standards.
Electrical and electronics calculators are built on Ohm's Law (V = IR), Watt's Law (P = IV), and the power formulas that connect voltage, current, resistance, and power. They extend to cable sizing, voltage drop, transformer ratios, capacitor charge/discharge, and three-phase power calculations — covering the calculations that electrical engineers, electricians, and electronics hobbyists encounter most frequently.
Civil and structural calculators handle the mechanical properties of beams, columns, and foundations. Beam deflection under uniformly distributed or point loads, moment of inertia for standard cross-sections, reinforced concrete design parameters, and soil bearing capacity are among the most commonly needed calculations in structural analysis. These tools use standard formulas from codes such as Eurocode, BS, and ACI.
Unit conversion is a daily requirement across all engineering disciplines where international teams, mixed-unit specifications, and legacy documentation create constant conversion needs. Our unit converters cover length, area, volume, mass, force, pressure, energy, power, temperature, and data units — with multi-step conversion chains handled automatically.
All engineering calculators use formulas from published standards and technical references. Results should be used as a design aid and starting point — final engineering calculations for safety-critical applications must be verified by a qualified engineer and may require formal documentation under the applicable building code or regulatory framework.
All Engineering Calculators (34)
Density Calculator
Calculate density, mass, or volume using the density formula D = M/V.
Pipe Weight Calculator
Calculate the weight of steel, PVC, or other pipe by outer diameter, thickness, and length.
Concrete Calculator
Estimate concrete volume and bags needed for slabs, footings, columns, and walls.
Steel Weight Calculator
Calculate the weight of steel bars, plates, pipes, and sections by dimensions.
Voltage Calculator
Calculate voltage using Ohm's Law (V = IR) or power equations (V = P/I).
Ohm's Law Calculator
Calculate voltage, current, resistance, or power using Ohm's Law and Watt's Law.
Watt Calculator
Calculate electrical power in watts from voltage and current, or resistance and voltage.
Resistance Calculator
Calculate total resistance for series and parallel resistor circuits.
Power Consumption Calculator
Estimate electricity cost by entering device wattage, usage hours, and electricity rate.
Fuel Consumption Calculator
Calculate fuel consumption rate, total fuel used, and fuel efficiency in L/100km or MPG.
Speed Calculator
Calculate speed, distance, or time using the formula Speed = Distance / Time.
Force Calculator
Calculate force, mass, or acceleration using Newton's Second Law (F = ma).
Torque Calculator
Calculate torque from force and lever arm length, or convert between torque units.
Pressure Calculator
Calculate pressure from force and area, or convert between pressure units.
Area Conversion Calculator
Convert between area units: sq meters, sq feet, acres, hectares, sq km, and more.
Unit Conversion Calculator
Convert between length, weight, temperature, volume, speed, and other units.
Material Cost Calculator
Estimate total material cost for construction or manufacturing projects by quantity and unit price.
Load Calculator
Calculate structural loads including dead load, live load, and total load per unit area.
Asphalt Calculator
Calculate the amount and cost of asphalt needed for driveways, roads, and parking lots.
Brick Calculator
Calculate the number of bricks needed for any wall with mortar joints.
Cement Calculator
Calculate the amount of cement bags, sand, and gravel needed for concrete or mortar mixes.
Tile Calculator
Calculate the number of tiles needed for any floor or wall area with grout lines and waste.
Flooring Calculator
Calculate flooring material needed for any room with waste factor and cost estimate.
Paint Calculator
Calculate the number of paint cans or litres needed to paint any room or surface.
Solar Panel Calculator
Calculate how many solar panels you need, estimated energy output, and payback period.
Battery Life Calculator
Calculate battery life, runtime, and capacity needed for any device or system.
Voltage Drop Calculator
Calculate voltage drop across cables and wires for electrical systems.
Cable Size Calculator
Calculate the correct cable size (cross-section area) for electrical installations.
Water Tank Calculator
Calculate water tank volume, capacity, and required size for household or commercial use.
Excavation Calculator
Calculate excavation volume, cut and fill quantities, and earthwork cost estimates.
Gravel Calculator
Calculate how much gravel, crushed stone, or fill material you need for any project.
Roofing Calculator
Calculate roofing materials, shingles, and cost for any roof pitch and area.
Stair Calculator
Calculate stair rise, run, number of steps, and stringer length for any total rise.
Beam Deflection Calculator
Calculate beam deflection and bending stress for simply supported and cantilever beams.
Engineering Calculator Guides
Electrical & Electronics
Ohm's Law: V = I × R; Watt's Law: P = V × I = I² × R = V² ÷ R. These four forms let you find any unknown (voltage, current, resistance, or power) given any two known quantities. The voltage divider rule: Vout = Vin × R2 ÷ (R1 + R2) is fundamental in both analogue circuit design and sensor interfacing.
Cable sizing requires calculating the current carrying capacity needed and the maximum permissible voltage drop. Voltage drop = I × L × R/m × 2 ÷ 1000 (for single-phase), where L is the one-way cable length in metres and R/m is the resistance per metre from cable manufacturer data. Most electrical codes limit voltage drop to 3–5% of supply voltage.
Structural & Civil
Beam deflection under a central point load: δ = PL³ ÷ (48EI); under a uniformly distributed load (UDL): δ = 5wL⁴ ÷ (384EI). E is the modulus of elasticity (Young's modulus) and I is the second moment of area of the cross-section. For a rectangular section: I = bh³ ÷ 12. These formulas are used to ensure deflection limits in building codes are not exceeded.
Concrete volume calculators help estimate the material needed for slabs, columns, footings, and beams, accounting for standard formwork dimensions. Rebar spacing and quantity calculators determine the number of reinforcement bars required to meet minimum reinforcement ratios specified in design codes. Use these for materials estimation — structural design must be validated by a structural engineer.
Unit Conversion
Unit conversion errors are a documented cause of engineering failures — most famously the loss of the Mars Climate Orbiter in 1999 due to a metric/imperial mix-up. Our unit converters support all SI and imperial units across length, area, volume, mass, pressure, force, torque, energy, power, and temperature. Multi-step conversions (e.g., BTU/h to watts to horsepower) are handled in a single input.
Temperature conversion: °C = (°F − 32) × 5/9; °F = °C × 9/5 + 32; K = °C + 273.15. Pressure: 1 bar = 100 kPa = 0.987 atm = 14.504 psi. Power: 1 horsepower = 745.7 W = 0.7457 kW. These are the most commonly needed conversions in mechanical and HVAC engineering.
Top Engineering Calculators
Beam Deflection Calculator
Calculate mid-span deflection for simply supported and cantilever beams under point loads and UDLs.
Ohm's Law Calculator
Find voltage, current, resistance, or power given any two known electrical quantities using Ohm's Law.
Cable Size Calculator
Calculate the correct cable cross-section based on load current, length, and permissible voltage drop.
Unit Converter
Convert between all common engineering units — length, mass, pressure, force, energy, power, and more.
Concrete Calculator
Estimate concrete volume and material quantities for slabs, columns, beams, and footings.
Key Formulas & References
Ohm's Law
V = I × R
V = voltage (V), I = current (A), R = resistance (Ω)
Watt's Law
P = V × I = I² × R = V² ÷ R
P = power (W); any two of V, I, R gives the fourth quantity
Beam Deflection (central load)
δ = P × L³ ÷ (48 × E × I)
Simply supported beam; E = Young's modulus, I = second moment of area
Rectangular I
I = b × h³ ÷ 12
Second moment of area for a rectangular section; b = width, h = depth
Frequently Asked Questions About Engineering Calculators
Ohm's Law states that voltage (V) equals current (I) multiplied by resistance (R): V = I × R. This relationship holds for most resistive components at constant temperature. The four derived forms — V = IR, I = V/R, R = V/I, and P = V × I — allow you to find any electrical quantity given two others.
For a simply supported beam with a central point load P, deflection at mid-span: δ = PL³ ÷ (48EI). For a UDL (w per unit length): δ = 5wL⁴ ÷ (384EI). E is the modulus of elasticity (200 GPa for steel, ~30 GPa for concrete) and I is the second moment of area of the cross-section. Always check the result against deflection limits in the applicable building code.
Voltage drop (single-phase) = I × L × (2 × R/m) ÷ 1000, where I is current in amps, L is one-way cable length in metres, and R/m is the resistance per metre from the cable data sheet (in mΩ/m). Most codes limit voltage drop to 3% (lighting) or 5% (power) of the nominal supply voltage.
Our engineering calculators accept both SI (metric) and imperial inputs. For structural calculations, we use SI units (Newtons, metres, Pascals) as required by Eurocode and BS standards. US-based calculations use imperial units (pounds, inches, psi) as per ACI and AISC standards. Unit selection is clearly indicated on each calculator.
Engineering calculators are suitable for preliminary sizing, feasibility studies, material estimation, and checking hand calculations. Safety-critical structural and electrical designs must be verified by a qualified and professionally registered engineer, and where required by law, formally signed off and documented under the applicable building code or regulatory framework.
For a rectangular cross-section: I = b × h³ ÷ 12, where b is the width and h is the depth (in the plane of bending). For a hollow rectangular section, subtract the I of the hole from the overall section. For I-beams and other standard profiles, use tabulated values from structural steel tables (e.g., Blue Book for UK, AISC Manual for US).
BrainyCalculators Editorial Team
Our Engineering calculators are researched, built, and reviewed by the BrainyCalculators editorial team using industry-standard formulas and validated against authoritative references. Results are updated whenever underlying standards, rates, or guidelines change. All calculators are free, require no account, and run entirely in your browser.