Engineering
Electrical, mechanical, civil and technical tools.
Free Calculators, Converters &
Engineering Tools
Fast, accurate tools for daily calculations, electrical work, solar design, finance and unit conversions.
Planning solar for your home or business?
Tamil Nadu & South India: estimate system size and generation, then request solar design or installation consultation.
உங்கள் EB bill-க்கு எத்தனை kW solar தேவை? கணக்கிட்டு, project enquiry அனுப்புங்கள்.
Solar calculators & project enquiry →Popular Tools
Frequently used calculators and converters
Browse by Category
Explore our calculators and tools by category
Solar
Solar design, energy yield and system calculators.
Finance
EMI, loan, investment and financial calculators.
Creator Tools
Image, PDF and content tools for creators.
File Tools
PDF, image and document converters and utilities.
Daily Life
Age, dates, grades and everyday calculators.
Unit Converters
Length, weight, temperature, currency and more.
Construction
Concrete, steel, bricks, paint and building costs.
Electrical
Cable sizing, voltage drop, transformers and earthing.
Health & Fitness
BMI, calories, body fat and fitness calculators.
Scientific & Math
Physics, chemistry, statistics and advanced maths.
Calendars
Tamil and English calendars, festivals and dates.
Vehicle & Auto
Fuel cost, mileage, EV and vehicle running costs.
Digital & Developer
Internet speeds, file sizes and networking tools.
Agriculture
Irrigation, water needs and practical farm planning.
Environment
Energy use, carbon footprint and sustainability.
Free to use
All tools are free and open to everyone.
Works instantly
No installation or downloads required.
Mobile friendly
Use on any device, anywhere.
No signup needed
Start using most tools right away.
Popular Articles
Useful guides recently read on OneCalcApp
Math
Dilution Ratios Explained: How to Calculate 1:10 to 1:1000 Mixes
What 1:N really means, how to convert any dilution ratio into ounces per gallon or ml per litre, worked examples from 1:10 to 1:1000, and a printable ratio chart.
Read guide SolarSolar Plant Earthing Design: IEEE 80 Calculation Guide with Worked 6 MW Example
How solar plant earthing is actually calculated: soil resistivity, grid current and division factor, conductor thermal sizing, Schwarz grid resistance, GPR, tolerable and attainable touch, mesh and step voltage, earth-pit quantity and transformer earthing.
Read guide SolarSolar PV Performance Ratio (PR): Complete Guide to PV System Losses
What performance ratio means, every loss term from temperature to availability, how the losses multiply, and how PR differs from efficiency and capacity factor.
Read guide AC Cable SizingFull Load Current Calculation – The Foundation of AC Cable Sizing
Learn how to calculate inverter Full Load Current using the three-phase power formula and understand every parameter involved in AC cable sizing.
Read guide SolarPV System Size Calculator: How to Calculate the Right Solar PV System Size
The full PV sizing chain — load, peak sun hours, performance ratio, required DC capacity, module count, inverter capacity and DC/AC ratio — with worked equations.
Read guide EngineeringHow Long Does It Take to Fill a Water Tank?
Calculate water tank filling time from tank volume and pump flow, with 500 L, 1000 L, 5000 L and 10000 L examples, required LPM and electricity use.
Read guideHelp Us Improve OneCalcApp
Ideas, bug reports and tool requests are welcome. No login required.