// NumberCals · one stop for checking a calculation
From Aryabhata to Algorithms — Calculators for the Curious
A free collection of teaching calculators that show their working. Pick a subject below, or open the standard or scientific calculator.
Explore by subject
Each subject is a folder on disk. Add a calculator and it appears here automatically — nothing here is hand-maintained.
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Maths
Algebra, trig, calculus, geometry.
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Physics
Mechanics, motion, electricity, thermo.
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Computers
Search algorithms, data structures, and how machines find things.
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Chemistry
Concentration, colligative properties, kinetics, equilibrium, and electrochemistry.
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Accounting
Interest, depreciation, finance.
📊
Business & Finance
Impact metrics, growth and money maths for business decisions.
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Real Estate
Advanced property investment, yield and cashflow simulation.
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Sports
Performance and impact metrics across football, basketball, cricket and more.
📈
Business Simulation
SaaS growth, funnel, pricing and unit-economics models.
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Engineering
Practical estimation tools for civil and structural work.
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Health
Body composition, energy, and fitness — every number shown with its working.
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Conversions
Units, measures, and constants — every domain.
Scientists & Scholars
The scientists and scholars whose laws and formulas power these tools — from Aryabhata to the present. Meet them →