Free · Ad-supported · No sign-up required
Master your field with verified calculation.
Precision, trust and provenance.
Medicine, finance or electronics — find the exact formula and a worked example. Every page prints the formula it uses, works the example through with the figures on screen, and cites the standard, textbook or datasheet it came from.
Stop guessing. Start verifying.
Calculator hub
- Calculators
- 957
- Categories
- 60
- Subjects
- 3
- The formula is on the pageNot just an answer — the equation it came from, written out, with the assumptions it rests on.
- Sources you can look upStandards, textbooks, clinical guidelines and manufacturer datasheets, named and dated where it matters.
- A worked example that matchesEvery page opens with real figures and shows the same sum worked through, so you can verify it in a minute.
- Free, and it stays in your browserAd-supported, no sign-up and no paywall. The arithmetic runs on your device — nothing you type is sent anywhere.
749 calculators · 30 categories
Medical Calculators
Clinical scores, dosing, unit conversions and lab interpretation, each with the rule it follows and where that rule comes from.
CKD-EPI 2021 Creatinine eGFR CalculatorEstimate GFR from creatinine, age and sex using the 2021 race-free CKD-EPI equation, the current standard for adults.Renal Function & eGFRCockcroft-Gault Creatinine Clearance CalculatorEstimate creatinine clearance in mL/min — the equation most drug labels specify for renal dose adjustment.Renal Function & eGFRAnion Gap CalculatorCalculate the serum anion gap from sodium, chloride and bicarbonate — with the interval that belongs to this…Acid-Base & Blood GasCorrected Calcium CalculatorAdjust total serum calcium for a low albumin using the traditional correction formula, and see why it should…Bone & Mineral MetabolismBody Surface Area (BSA) CalculatorCalculate BSA by the Mosteller or Du Bois formula, the basis of most chemotherapy dosing and of eGFR…Tumour Markers & Oncology LabsLDL Cholesterol Calculator (Friedewald)Estimate LDL cholesterol from total cholesterol, HDL and triglycerides using the Friedewald equation — and see the four…Lipids & Cardiovascular Risk Labs
Acid-Base & Blood Gas 22Adrenal & Steroid Hormones 24Amino Acids, Metabolic & Newborn Screening 33Blood Bank & Transfusion Medicine 20Bone & Mineral Metabolism 21CSF & Body Fluid Analysis 23Cardiac Markers 19Chemistry & Electrolytes 29Coagulation & Thrombosis 23Diabetes, Glucose & Insulin Resistance 30Haematology — Red Cell & Indices 24Haematology — White Cell & Inflammatory Ratios 24Immunology, Autoantibodies & Complement 28Infectious Disease & Sepsis Labs 22Iron Studies 24Lab Utilities, Dilutions & Unit Tools 21Laboratory Quality, Statistics & Interpretation 24Lipids & Cardiovascular Risk Labs 25Liver & Gastrointestinal 33Molecular, Genetics & Specimen Calculations 24Neonatal & Paediatric Laboratory 24Pituitary, Gut & Metabolic Hormones 22Renal Function & eGFR 27Reproductive, Fertility & Pregnancy Labs 30Therapeutic Drug Monitoring 30Thyroid 24Toxicology & Poisoning 26Tumour Markers & Oncology Labs 22Urine Chemistry & Urinalysis 24Vitamins, Trace Elements & Nutrition Labs 27
154 calculators · 12 categories
Finance Calculators
Loans, savings, investments and salary, in twelve currencies, with the formula and the assumptions on the page.
EMI CalculatorWork out the monthly instalment on a home, car, personal or education loan from the amount, interest rate…Loans & EMISIP CalculatorEstimate what a monthly SIP could grow to at an assumed annual return, and how much of it…Investing & Mutual FundsFD Calculator (Fixed Deposit)What a fixed deposit pays: the maturity value if interest is reinvested, or the interest paid out each…Savings & DepositsHome Loan Eligibility CalculatorHow large a home loan can you afford? Start from the EMI you are comfortable paying — or…Loans & EMICompound Interest CalculatorGrow a lump sum, with optional monthly additions, at any compounding frequency — and see how much of…Savings & DepositsGratuity Calculator (India)Gratuity under India's Code on Social Security, 2020: 15 days' wages for each year of service, using your…Salary & Employee Benefits
54 calculators · 18 categories
Electronics Calculators
From Ohm's law to solar sizing, most with a live circuit diagram that redraws as you type.
Ohm’s Law CalculatorEnter any two of voltage, current, resistance and power and get the other two, with units scaled automatically…Basic Circuit LawsLED Series Resistor CalculatorThe resistor an LED needs: exact value, the next standard value up, the current you actually get with…LEDs & LightingResistor Color Code CalculatorPick the colour of each band on a 4-, 5- or 6-band resistor and read its resistance, the…Component Codes & ValuesElectricity Consumption Calculator (Units per Month)Add up to six appliances — watts, hours a day and how many you own — and see…Wiring, Cables & Home ElectricalInverter Battery Backup Time CalculatorHow many hours your inverter will run on its battery: from the bank's Ah and voltage, the usable…Batteries, UPS & SolarVoltage Drop CalculatorThe voltage a cable loses at your load current — in volts and as a percentage — with…Wiring, Cables & Home Electrical
Basic Circuit Laws 3Batteries, UPS & Solar 7Capacitors, Inductors & Reactance 3Component Codes & Values 3DC-DC Converters 6Electrical Unit Converters 2Filters & Frequency Response 1LEDs & Lighting 1Linear Power & Regulators 3Magnetics & Transformers 1Motors & Drives 1Op-Amps & Analog 4PCB Design 1Power Semiconductors & Thermal 3RF, Antennas & Transmission Lines 2Sensors & Thermistors 1Timers, Oscillators & Digital 3Wiring, Cables & Home Electrical 9
Recently added
- Zener Diode Regulator CalculatorElectronics
- Capacitive and Inductive Reactance CalculatorElectronics
- Comparator Hysteresis (Schmitt Trigger) CalculatorElectronics
- Series and Parallel Resistor CalculatorElectronics
- SMD Resistor Code CalculatorElectronics
- Op-Amp Inverting Amplifier CalculatorElectronics
- Op-Amp Non-Inverting Amplifier CalculatorElectronics
- PWM Duty Cycle and Average Voltage CalculatorElectronics
How these calculators are built
Each calculator is a page of arithmetic with its reasoning shown. The formula is printed, the worked example matches the figures the page opens with, and the references name the textbook, standard or manufacturer datasheet the numbers came from.
Nothing here is advice. A medical calculator does not know your patient, a financial one does not know your tax position, and an electronics one does not know your local wiring code. Use the result as a check on your own working, and take the decision with someone qualified to make it.