Calculators
Free online calculators for circuit design, finance, health, math, cooking, marketing, and business decisions.
Featured calculators
High-intent tools with formulas, examples, assumptions, and related calculators.
Voltage Divider Calculator
voltage divider calculator
Open Calculator โParallel Resistor Calculator
parallel resistor calculator
Open Calculator โResistor Network Calculator
series resistor calculator
Open Calculator โOhm's Law Calculator
ohm's law calculator
Open Calculator โMortgage Calculator
mortgage calculator
Open Calculator โCompound Interest Calculator
compound interest calculator
Open Calculator โPercentage Calculator
percentage calculator
Open Calculator โBMI Calculator
bmi calculator
Open Calculator โCalorie Calculator
tdee calculator
Open Calculator โSquare Footage Calculator
square footage calculator
Open Calculator โElectricity Cost Calculator
electricity cost calculator
Open Calculator โWire Size Calculator
wire size calculator
Open Calculator โFinancial
Finance calculators for payment, interest, price, salary, discount, and tax decisions. Each tool shows assumptions and keeps estimates separate from advice.
Mortgage Calculator
Calculate monthly payments, total interest, and view amortization schedule.
Open Calculator โTip Calculator
Calculate tip amount and split the bill between multiple people.
Open Calculator โCompound Interest Calculator
Calculate how your investment grows over time with compound interest and optional regular contributions.
Open Calculator โLoan Calculator
Calculate monthly payments, total interest, and total cost on personal loans.
Open Calculator โSales Tax Calculator
Calculate sales tax amount and total price for any US state or custom rate.
Open Calculator โDiscount Calculator
Calculate discount amounts and final prices with percentage or dollar-off discounts.
Open Calculator โSalary Calculator
Convert between annual, monthly, biweekly, weekly, and hourly pay rates.
Open Calculator โElectrical
Circuit calculators for real design checks: resistor networks, voltage dividers, Ohm's law, LED limiters, wire sizing, voltage drop, filters, timing, batteries, and AC power.
Electricity Cost Calculator
Estimate the cost of running appliances based on wattage, usage hours, and electricity rate.
Open Calculator โOhm's Law Calculator
Calculate voltage, current, resistance, or power from any two known values using Ohm's Law and power formulas.
Open Calculator โPower Calculator
Calculate electrical power. Convert watts to amps, amps to watts, and volts to watts for DC, single-phase, and three-phase AC circuits.
Open Calculator โWire Size Calculator
Find the minimum wire gauge (AWG) for a given load based on NEC 310.16 ampacity tables and voltage drop limits.
Open Calculator โVoltage Drop Calculator
Calculate voltage drop over a wire run for single-phase or three-phase circuits, based on wire gauge, distance, and current.
Open Calculator โResistor Color Code Calculator
Decode resistor values from 4, 5, or 6 color bands, or find the color code for any resistance value and tolerance.
Open Calculator โVoltage Divider Calculator
Solve for output voltage or either resistor in a two-resistor divider, with optional load to show the real-world loading effect.
Open Calculator โParallel Resistor Calculator
Find equivalent resistance for two or more resistors in parallel, with optional voltage to calculate total current and power.
Open Calculator โLED Resistor Calculator
Calculate the current-limiting resistor for an LED or LED chain from supply voltage, forward voltage, and forward current.
Open Calculator โBattery Life Calculator
Estimate how long a battery lasts from its capacity, the load it drives, efficiency, and an optional Peukert correction.
Open Calculator โ555 Timer Calculator
Calculate frequency, period, duty cycle, and pulse width for the 555 timer IC in astable (oscillator) or monostable (one-shot) mode.
Open Calculator โResistor Network Calculator
Combine up to 10 resistors in series or parallel. Live SVG schematic, total resistance, conductance, and optional current and power from an applied voltage.
Open Calculator โRC Filter Calculator
Design a first-order RC low-pass or high-pass filter. Solve for cutoff frequency, capacitance, or resistance, and read attenuation and phase at any probe frequency.
Open Calculator โPower Factor Calculator
Calculate AC power factor, phase angle, apparent power, and reactive power. Size correction capacitors to improve PF for single-phase or three-phase systems.
Open Calculator โInductance Calculator
Combine inductors in series or parallel, and calculate stored energy, inductive reactance, and RL time constant. Live SVG schematic, smart unit formatting.
Open Calculator โCapacitance Calculator
Combine capacitors in series or parallel, and calculate stored charge Q = CV, energy E = ยฝCVยฒ, and the RC time constant. Live SVG schematic, smart unit formatting.
Open Calculator โHealth
Health and fitness calculators for screening, training, nutrition, pregnancy, and workout planning, with practical limits and safety disclaimers built in.
BMI Calculator
Calculate your Body Mass Index and see your weight category.
Open Calculator โCalorie Calculator
Calorie and TDEE calculator. Find your Total Daily Energy Expenditure and BMR with Mifflin-St Jeor and Harris-Benedict equations, plus macronutrient breakdown for your caloric goals.
Open Calculator โPace Calculator
Calculate running pace, time, or distance. Enter any two values to find the third, with split times for your run.
Open Calculator โPregnancy Calculator
Pregnancy and due date calculator. Estimate your due date from last menstrual period or conception date, with week-by-week pregnancy timeline.
Open Calculator โHeart Rate Zones Calculator
Calculate your five heart rate training zones using standard (220 minus age) or Karvonen (heart rate reserve) methods.
Open Calculator โOne Rep Max (1RM) Calculator
Estimate your one-rep max from submaximal lifts using Epley, Brzycki, Lombardi, Mayhew, and Wathan formulas. Includes training load percentage chart.
Open Calculator โMath
Everyday math calculators for percentages, fractions, and area tasks where a fast answer plus the underlying formula matters.
Percentage Calculator
Calculate percentages, percentage change, and more.
Open Calculator โFraction Calculator
Add, subtract, multiply, and divide fractions with step-by-step working shown.
Open Calculator โSquare Footage Calculator
Calculate the area of rooms and spaces from dimensions. Supports multiple shapes and multi-room totals.
Open Calculator โDate & Time
Date and age calculators for deadlines, durations, birthdays, schedules, and calendar math.
Cooking
Cooking calculators for substitutions and recipe adjustments when the right ratio matters more than a rough guess.
Marketing
Marketing calculators for campaign efficiency: ROAS, CPC, and CPM with clear formulas for spend and performance checks.
ROAS Calculator
Calculate Return on Ad Spend (ROAS) from revenue and ad spend, or solve for the missing input. Shows ratio, percentage, and break-even status.
Open Calculator โCPC Calculator
Calculate Cost Per Click (CPC) from total cost and clicks, or solve for the missing input. The IAB standard pricing metric for paid search and performance advertising.
Open Calculator โCPM Calculator
Calculate Cost Per Mille (CPM) from total cost and impressions, or solve for the missing input. The IAB standard pricing metric for impression-based advertising.
Open Calculator โBusiness
Business calculators for pricing, margins, break-even points, and profitability checks.
Markup Calculator
Calculate markup percentage, selling price, or cost. Includes margin-to-markup converter and shows gross margin, profit, and price multiplier.
Open Calculator โBreak-Even Calculator
Calculate the break-even point in units, fixed costs, selling price, or variable cost per unit. Shows contribution margin and break-even revenue.
Open Calculator โProfit Margin Calculator
Calculate gross, operating, and net profit margins from revenue and costs. Solve for revenue or COGS at a target margin.
Open Calculator โ