Calculate acoustic impedance for two materials and find reflection and transmission coefficients at the interface. Used in ultrasound, sonar, and acoustic design.

Big Mac Index Calculator

Compare currency purchasing power using the Big Mac Index. Enter prices in two countries to see implied exchange rate and currency over- or undervaluation.

Cobb-Douglas Production Function

Calculate output, marginal products, and returns to scale using the Cobb-Douglas production function Y = A x K^alpha x L^(1-alpha). Standard model in macroeconomics.

Consumer Price Index (CPI) Calculator

Calculate CPI and inflation rate from a basket of goods. Enter quantities and prices for up to three items in base and current periods to measure price level changes.

Cournot Duopoly Nash Equilibrium Calculator

Calculate Nash equilibrium output, market price, and firm profits for a two-firm Cournot duopoly with linear demand and constant marginal costs.

Hotelling Rule Resource Price Calculator

Apply Hotelling's rule to find the optimal price path for an exhaustible resource. Shows how the royalty grows at the rate of interest over time.

Money Supply Calculator (M1, M2, M3)

Break down money supply into M1 and M2 components. Enter currency, demand deposits, savings, and money market balances to calculate each monetary aggregate.

Paris Law Fatigue Crack Growth Calculator

Calculate fatigue crack growth rate and cycles to failure using the Paris-Erdogan law. Enter material constants C and m, stress range, and crack sizes to find cycles to failure.

Pressure Vessel Stress Calculator

Calculate hoop stress, longitudinal stress, and Von Mises equivalent stress in thin-walled pressure vessels. Enter internal pressure, vessel diameter, and wall thickness.

Stress Concentration Factor Calculator

Calculate stress concentration factor Kt for a circular hole in a finite-width plate under tension. Find peak stress at the hole edge using Peterson's formula.

Venturi Flow Meter Calculator

Calculate volumetric flow rate from differential pressure in a Venturi meter. Enter pipe diameter, throat diameter, pressure drop, and fluid density to find flow velocity and rate.

Earthquake Epicenter Intensity Calculator

Estimate Modified Mercalli Intensity (MMI) at your location based on earthquake magnitude and distance from the epicenter.

Heat Transfer Fin Efficiency Calculator

Calculate fin efficiency and heat transfer rate for rectangular fins using the hyperbolic tangent method. Enter fin geometry, thermal conductivity, and convection coefficient.

Laffer Curve Tax Revenue Calculator

Model how tax revenue changes across different tax rates. Find the revenue-maximizing rate and visualize the Laffer curve trade-off between rate and economic base.

Phillips Curve Inflation Calculator

Estimate inflation using the Phillips curve trade-off between unemployment and price levels. Enter expected inflation, NAIRU, sensitivity, and current unemployment rate.

Solow Growth Model Steady State

Calculate Solow model steady-state capital and output per worker. Enter savings rate, depreciation, and capital share to find the long-run growth equilibrium.

Spring-Mass Natural Frequency Calculator

Find the natural frequency, angular frequency, and resonant period of a spring-mass system. Add damping to compute damped natural frequency and damping ratio.

Belt Drive Ratio Calculator

Calculate driven pulley RPM, torque ratio, and belt length for a two-pulley belt drive. Useful for HVAC, machine tools, and power transmission design.

Bolt Tensile Strength Calculator

Calculate maximum tensile load and proof load for a bolt from diameter, thread pitch, and grade. Supports SAE Grade 5, Grade 8, and metric bolts.

Chain Drive Speed Calculator

Calculate driven sprocket RPM, chain speed, and ratio for a roller chain drive. Used for motorcycles, bicycles, conveyors, and industrial drives.

Inclined Plane Calculator

Calculate effort force, mechanical advantage, and friction loss on an inclined plane (ramp). Useful for loading docks, ADA ramps, and physics homework.

Lever Mechanical Advantage Calculator

Calculate lever effort force, fulcrum-to-effort and fulcrum-to-load arm lengths. Supports class 1, class 2, and class 3 lever configurations.

Pulley Mechanical Advantage Calculator

Calculate mechanical advantage, lift force, and rope distance for a pulley system. Supports fixed, movable, and block-and-tackle multi-pulley setups.

Darcy-Weisbach Friction Loss Calculator

Calculate pipe friction head loss using the Darcy-Weisbach equation. Includes Reynolds number, Darcy friction factor, and pressure drop in Pa and kPa.

Isentropic Flow Calculator

Calculate isentropic flow ratios — temperature, pressure, density, and area — for compressible nozzle flow at any Mach number and specific heat ratio.

Mach Number Calculator

Calculate Mach number from speed and air temperature. Covers subsonic, transonic, supersonic, and hypersonic regimes with speed-of-sound formula.

Van der Waals Gas Calculator

Calculate real gas pressure, temperature, or volume using the Van der Waals equation. Presets for CO2, N2, H2O, O2, CH4, and other common gases.

401(k) Employer Match Optimizer Calculator

Maximize your 401(k) employer match. Enter salary, contribution percentage, and match formula to see free-money capture rate and optimal contribution level.

I-Bond Real Yield Calculator

Calculate Series I Savings Bond real return after inflation and taxes. Compare I-Bond yield to TIPS, Treasuries, and HYSA for inflation-protected income.

Investment Risk Tolerance Score Calculator

Score your investment risk tolerance with a 7-question survey. Get a personal risk score, recommended portfolio asset allocation, and stocks-vs-bonds split.

Plate Tectonic Motion Distance Calculator

Calculate distance moved by a tectonic plate over geologic time. Enter rate and time span to see kilometers, miles, and equivalent landmark distances on Earth.

REIT Dividend Yield Calculator

Calculate REIT dividend yield, FFO multiple, and total return. Compare equity REITs against your target yield with quarterly distribution analysis.

Tax-Loss Harvesting Savings Calculator

Calculate tax savings from tax-loss harvesting your investments. Get federal and state savings, ordinary-income offset, and carryforward by tax bracket.

Money Multiplier Calculator

Calculate the banking money multiplier from reserve requirements. See how much money banks create from a monetary base through lending and credit expansion.

Unit Labor Cost Calculator

Calculate unit labor cost from wages and worker output. Compare two periods to measure competitiveness and track changes in labor productivity over time.

Bond Yield to Maturity (YTM) Calculator

Calculate bond yield to maturity from price, face value, coupon rate, and time to maturity. Find the true annualized return of any bond investment.

Dividend Reinvestment (DRIP) Calculator

See how reinvesting dividends accelerates wealth growth. Compare portfolio value with DRIP vs without over time — and calculate total dividends received.

Dollar Cost Averaging (DCA) Calculator

Calculate your average cost basis investing the same amount regularly. See how DCA reduces risk over time with total invested versus current portfolio value.

Portfolio Sharpe Ratio Calculator

Calculate the Sharpe ratio of your portfolio to measure risk-adjusted return. Compare how much return you are earning per unit of risk taken.

Retirement Withdrawal Rate Calculator

Calculate how long your retirement portfolio will last using the 4% rule or a custom withdrawal rate. See yearly portfolio balance over time.

Aggregate Demand Calculator (C + I + G + NX)

Calculate aggregate demand using AD = C + I + G + NX. Shows each component share of total demand with a breakdown of consumption, investment, and trade.

Comparative Advantage Calculator

Calculate comparative advantage and opportunity cost between two producers or countries to determine who should specialize in what.

Cost-Benefit Analysis Calculator

Calculate net present value, benefit-cost ratio, and payback period for a project or investment decision using CBA methodology.

Market Equilibrium Calculator

Find equilibrium price and quantity from linear supply and demand equations. See what happens when supply or demand shifts.

Pigouvian Tax (Externality) Calculator

Calculate the optimal Pigouvian tax needed to correct a negative externality and restore the socially efficient output level.

Purchasing Power Parity (PPP) Exchange Rate Calculator

Calculate the PPP-implied exchange rate between two countries and compare it to the market rate to find over- or undervaluation.

Aquifer Transmissivity and Hydraulic Conductivity Calculator

Calculate aquifer transmissivity T = K × b, Darcy velocity, and groundwater discharge using standard hydrogeology formulas and pumping test inputs.

Break-Even Point Calculator

Calculate the break-even point in units and revenue. Find out how many units you must sell to cover all fixed and variable costs.

Cantilever Beam Deflection Calculator

Calculate deflection, bending moment, and reaction forces in a cantilever beam with a point load. Supports rectangular sections or custom moment of inertia.

Crypto Portfolio Rebalancing Calculator

Calculate buy and sell amounts to rebalance a crypto portfolio back to target allocations. Enter current holdings and target weights to get a rebalancing plan.

Deadweight Loss Calculator

Calculate the deadweight loss caused by price floors, price ceilings, or per-unit taxes. Measure the welfare cost of market distortions.

Earthquake Magnitude Calculator

Calculate moment magnitude Mw from seismic moment or Richter scale. Returns energy in joules, TNT equivalent in kilotons, and Mercalli intensity description.

Euler Column Buckling Calculator

Calculate the critical Euler buckling load for slender columns from end conditions, material, and cross-section to find the load at which buckling occurs.

Gear Train Ratio Calculator

Calculate overall gear ratio, output speed, and torque for a compound gear train with up to 3 gear pairs. Enter RPM, torque, and tooth counts per stage.

Geologic Time Scale Calculator

Look up geologic eon, era, period, and epoch for any age in years, Ma, or Ga. Returns ICS classification and life forms from the Hadean to the Holocene.

Gini Coefficient Calculator

Calculate the Gini coefficient to measure income or wealth inequality. Enter income shares by group to compute the Gini index and plot the Lorenz curve.

Heat Conduction Calculator (Fourier Law)

Calculate heat flux and thermal resistance through a wall using Fourier's Law. Enter thermal conductivity, thickness, area, and temperature difference.

Hydraulic Cylinder Force Calculator

Calculate the extension and retraction force of a hydraulic cylinder using bore diameter, rod diameter, and hydraulic pressure. Results in kN and lbf.

Inflation Purchasing Power Calculator

Calculate how inflation erodes purchasing power over time. See the real value of money in future dollars and the percentage lost to inflation.

Keynesian Multiplier Effect Calculator

Calculate the Keynesian spending multiplier and its total impact on GDP. See how an initial injection ripples through the economy round by round.

Mineral Hardness Identification Guide

Identify minerals by Mohs hardness (1-10), streak color, and luster. Includes household scratch tests for each hardness level and a table of 30 minerals.

Price Elasticity of Supply Calculator

Calculate the price elasticity of supply (PES) using the standard or midpoint method. Determine if supply is elastic, inelastic, or unit elastic.

Sediment Particle Size Classifier (Wentworth Scale)

Classify sediment by the Wentworth scale from diameter in mm or micrometers. Returns phi (φ) value, class from clay to boulders, and Stokes settling velocity.

Slope Stability Factor of Safety Calculator

Calculate slope factor of safety (FS) via the infinite slope method. Enter angle, cohesion, friction angle, and groundwater depth. FS above 1.5 is stable.

Soil Bearing Capacity Calculator

Calculate ultimate and allowable soil bearing capacity using the Terzaghi method. Enter cohesion, friction angle, and depth to get safe foundation loads.

Stress and Strain Calculator

Calculate normal stress, strain, and elastic deformation using Young's modulus. Select from common engineering materials or enter a custom modulus.

Velocity of Money Calculator

Calculate the velocity of money using the Fisher equation (MV = PQ). Find how fast money circulates or the money supply needed for any target velocity.

Wire Ampacity and Current Rating Calculator

Look up NEC ampacity of copper and aluminum wire by AWG gauge, temperature rating, and installation method. Applies conductor count correction factors.

Accounting Profit vs Economic Profit Calculator

Calculate accounting profit and economic profit. Understand the difference between explicit costs, implicit costs, and opportunity cost in business decisions.

Centrifugal Pump Power Calculator

Calculate centrifugal pump hydraulic power, shaft power, efficiency, and NPSH. Find flow rate, head, specific speed, and motor sizing for pump selection.

Common Stock Book Value Calculator

Calculate book value per share of common stock and the price-to-book (P/B) ratio to evaluate whether a stock is potentially undervalued or overvalued.

Consumer Surplus Calculator

Calculate consumer surplus using the linear demand triangle formula or a manual demand schedule. Understand economic welfare and willingness to pay.

Darcy's Law Groundwater Flow Calculator

Calculate groundwater flow rate using Darcy's Law. Find seepage velocity, hydraulic gradient, and transmissivity for aquifers and porous media.

Flow Coefficient Cv Calculator

Calculate flow coefficient Cv (or Kv) for control, ball, and globe valves. Size valves for liquid and gas service using the ISA S75.01 standard formula.

GDP Deflator Calculator

Calculate the GDP deflator, real GDP, nominal GDP, or inflation rate between two years. Includes comparison with CPI and context on real vs nominal GDP growth.

GDP per Capita Calculator

Calculate GDP per capita (nominal or PPP-adjusted), compare living standards across countries, and measure year-over-year growth.

Labor Force Participation Rate Calculator

Calculate the labor force participation rate (LFPR) from employment, unemployment, and working-age population figures. Includes US historical context.

Lava Flow Volume Estimator

Calculate lava flow volume in m³ and km³ from length, width, and thickness. Includes effusion rate mode and mass calculation for basalt, andesite, or rhyolite.

LMTD Heat Exchanger Calculator

Calculate heat exchanger duty using LMTD. Find heat transfer rate, required area, and correction factor for shell-and-tube and counterflow heat exchangers.

Marginal Utility Calculator

Calculate marginal utility from total utility values. Find the point of maximum utility, diminishing returns, and display a complete MU table.

Moment of Inertia for Standard Cross-Sections

Calculate second moment of area (moment of inertia), section modulus, and radius of gyration for rectangle, circle, I-beam, T-section, and more.

National Income Calculator

Calculate national income using the income approach (wages, rent, interest, profit) or the expenditure approach (GDP minus depreciation and indirect taxes).

Orbital Insertion Delta-V Calculator

Calculate Hohmann transfer delta-v budget between two circular orbits around Earth, Mars, Moon, or Jupiter. Includes both burns and total delta-v in km/s.

Ore Grade and Contained Metal Calculator

Calculate contained metal tonnage from ore grade and ore tonnage. Convert between g/t, ppm, and percent for gold, silver, copper, and other metals in mining.

PID Controller Tuning Calculator (Ziegler-Nichols)

Calculate PID controller gains (Kp, Ki, Kd) using Ziegler-Nichols tuning rules. Supports step response and ultimate gain methods for P, PI, and PID controllers.

Planetary Gear Set Calculator

Calculate planetary gear ratio, output speed, and torque from ring, sun, and planet gear teeth. Covers all three fixed-member configurations.

Price Elasticity of Demand Calculator

Calculate price elasticity of demand (PED), income elasticity (YED), and cross-price elasticity (XED) using the standard or midpoint method.

Producer Surplus Calculator

Calculate producer surplus from supply curve data. Understand economic welfare, profit relationships, and total market surplus with this economics calculator.

Real vs Nominal GDP Calculator

Convert between real and nominal GDP using the GDP deflator. Also calculate GDP growth rate between two years. Includes worked examples.

Rock and Mineral Density Calculator

Look up density of common rocks and minerals. Calculate mass from volume or volume from mass. Compare granite, limestone, basalt, sandstone, and ore densities.

Seismic Energy Calculator

Calculate earthquake energy in joules from magnitude (Mw). See TNT equivalent, Hiroshima bomb equivalents, and comparison to historical earthquakes.

Shaft Power and Torque Calculator

Calculate shaft power from torque and RPM. Convert between horsepower, kilowatts, torque in Nm and lb·ft. Find torque from power or speed from torque and power.

Spring Rate Calculator

Calculate spring constant k, deflection, and force using Hooke's Law. Find coil spring rate from wire diameter, coil diameter, and number of active coils.

Steam Properties Calculator

Calculate steam properties at any temperature or pressure. Find saturation temperature, enthalpy, entropy, specific volume, and latent heat of vaporization.

System Stability Margin Calculator

Calculate gain margin and phase margin stability classifications for control systems. Find damping ratio, step overshoot, and stability rating.

Total Surplus Calculator

Calculate consumer surplus, producer surplus, and total economic surplus using supply and demand curve intercepts and equilibrium values.

Transfer Function Gain and Phase Calculator

Calculate gain and phase of a transfer function at any frequency. Supports first-order, second-order, and common filter forms for Bode plot analysis.

Volcano Eruption Energy Calculator

Calculate the energy released by volcanic eruptions. Convert between Volcanic Explosivity Index (VEI), erupted volume, and equivalent TNT or nuclear bomb yield.

Beam Bending Stress Calculator

Calculate the maximum bending stress in a simply supported beam under point or distributed loads. Essential for structural engineering.

Pipe Flow Rate Calculator

Calculate pipe flow rate in GPM, m³/h, and L/min from pipe diameter and fluid velocity. Includes Darcy-Weisbach pressure drop and Reynolds number.

Speeds and Feeds Calculator (CNC Machining)

Calculate CNC speeds and feeds: RPM from surface footage and diameter, feed rate from chip load and flutes. Covers milling, drilling, and turning.