RubanTools

Free Engineering Calculators for Civil & Electrical Engineers

17 curated tools for engineers - IS-standard concrete mix, beam deflection, wire sizing, Ohm's law, unit converters and project finance calculators.

Ohm's Law Calculator

Calculate voltage, current, resistance or power using Ohm's Law. Enter any two values and instantly get the other two. Supports V, A, Ohm and W with unit multipliers.

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Electrical Load Calculator

Calculate electricity consumption (kWh) and monthly bill for your home or office. Add appliances with wattage and hours per day to get daily units, monthly units, bill estimate and required MCB rating.

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Concrete Mix Calculator

Calculate cement bags, sand and aggregate quantities for M15, M20, M25 and M30 concrete grades using IS 10262 nominal mix method. Enter volume in cubic metres and get full material requirements.

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Beam Deflection Calculator

Calculate maximum deflection and bending moment for simply supported and cantilever beams under UDL or point load. Checks deflection against IS 456 permissible limits (L/250, L/350).

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Wire & Cable Size Calculator

Find the right cable cross-section (mm2) for any electrical load. Enter current, material (copper/aluminium) and installation method to get IS 694 based recommendations with derating factors.

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Length Converter

Convert between mm, cm, m, km, inches, feet, yards, miles and nautical miles - all units shown instantly.

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Area Converter

Convert sq ft, sq m, acre, hectare, ground, cent, bigha, kanal, marla and 5 more area units.

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Weight Converter

Convert between mg, g, kg, quintal, tonne, lb, oz and stone - all results shown at once.

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Pressure Converter

Convert Pascal, bar, psi, atm, mmHg, kPa, MPa, torr, inHg and mbar instantly.

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Energy Converter

Convert joule, kilojoule, calorie, kcal, Wh, kWh, BTU, eV and erg - all at once.

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Power Converter

Convert watt, kilowatt, megawatt, horsepower (metric & electric) and BTU/hr.

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Volume Converter

Convert between mL, litre, gallon (US/UK), cup, tablespoon, teaspoon, fl oz, quart and pint.

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Temperature Converter

Instantly convert between Celsius, Fahrenheit and Kelvin with exact formula output.

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Scientific Calculator

Full scientific functions - sin, cos, log, powers, roots, π and more. Respects BODMAS with a proper expression evaluator.

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Percentage Calculator

Three modes in one: find X% of a number, find what % one value is of another, or calculate % increase or decrease.

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Stamp Duty Calculator

Calculate property stamp duty and registration charges for 14 major Indian states with female buyer concessions.

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EMI Calculator

Calculate monthly EMI, total interest and full amortisation schedule for any loan with reducing-balance formula.

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Engineering Calculator Tools

India produces over 1.5 million engineering graduates annually, making it one of the largest engineering workforces in the world. From civil and structural engineers working on infrastructure projects under PMGSY and Smart Cities Mission to electrical engineers designing industrial installations per Bureau of Indian Standards (BIS) codes, accurate calculation tools are indispensable on the job. This collection brings together the most commonly needed engineering calculators built around Indian standards such as IS 456, IS 10262, and IS 694.

Civil and Structural Calculations

Civil engineers in India routinely calculate concrete mix proportions per IS 10262:2019 and beam deflections under IS 456:2000, the code governing reinforced cement concrete design. Stamp duty calculations are essential for property registrations across states - rates vary from 3% in Maharashtra to 7% in Karnataka. EMI calculators help project managers and procurement officers plan equipment finance, while unit converters bridge the gap between SI and legacy measurement systems still used in older drawings and contracts.

Electrical Engineering Tools

Ohm's law calculators, electrical load estimators, and wire gauge tools (based on IS 694 standards for PVC insulated cables) support electricians and electrical engineers in designing safe residential and industrial wiring. GATE and ESE exam aspirants preparing for quantitative electrical problems also benefit from quick calculation tools that verify manual working. All calculators on this platform are free, browser-based, and require no installation or login.

Engineering Calculators FAQ

IS 10262:2019 - Concrete Mix Proportioning: Guidelines - published by the Bureau of Indian Standards governs concrete mix design in India. For nominal mixes, the standard prescribes cement:fine aggregate:coarse aggregate ratios by volume: M15 is 1:2:4, M20 is 1:1.5:3, M25 is 1:1:2, and M30 is 1:0.75:1.5. The water-cement ratio for nominal mixes is typically 0.5. To compute material quantities, the wet volume of concrete is multiplied by a dry volume factor of 1.54 to account for bulking and voids. Our concrete mix calculator applies these IS 10262 ratios and returns cement bags, sand weight and coarse aggregate weight for any pour volume with a 10% procurement wastage buffer.

IS 456:2000 - Plain and Reinforced Concrete Code of Practice - Clause 23.2 specifies deflection limits for beams. The final deflection due to all loads including the effects of temperature, creep and shrinkage should not exceed span/250. The deflection occurring after the erection of partitions and finishes should not exceed span/350 or 20 mm whichever is less to prevent damage to non-structural elements. Our beam deflection calculator applies the span/250 limit check against the theoretical elastic deflection computed using standard formulas for simply supported beams under UDL (5wL4/384EI) and point load (PL3/48EI), and cantilever beams under UDL (wL4/8EI) and point load (PL3/3EI).

IS 694:2010 - PVC Insulated Cables for Working Voltages up to and including 1100V - published by BIS specifies current-carrying capacity (ampacity) for copper and aluminium conductors under standard reference conditions (30 degrees C ambient, cables in free air). For practical installations, derating factors are applied for: installation method (clipped to surface, in conduit, underground, bunched in tray), ambient temperature above 30 degrees C, and grouping of multiple circuits. Our wire gauge calculator uses the IS 694 reference ampacity table for copper conductors (1 mm2 to 240 mm2) with an aluminium correction factor of 0.78, and applies the installation method derating so you can find the minimum safe cable size for any full-load current.

Ohm's Law states that the voltage across a conductor is directly proportional to the current flowing through it: V = I x R, where V is voltage in volts, I is current in amperes, and R is resistance in ohms. The four derived relationships are: V = IR, I = V/R, R = V/I, and P = VI (power in watts). Extended power formulas are: P = I2R and P = V2/R. For AC circuits, apparent power S = V x I (in VA), real power P = S x power factor (in W), and reactive power Q = sqrt(S2 - P2) (in VAR). Our Ohm's law calculator accepts any two of V, I, R and computes the remaining values along with power dissipation for both DC and single-phase AC circuits.