All Calculators

Find the original value before a percentage increase or decrease, or work out what number a value is a given percentage of.

Calculate the area, side length, and perimeter of a rhombus from its two diagonals — area = (d1 × d2) ÷ 2.

Convert a ring's inner diameter in millimetres to US and EU/ISO ring sizes, with the inner circumference shown alongside.

Solve for the unknown value in a proportion using the rule of three (Dreisatz), with support for both direct and inverse relationships.

Calculate your total SAT score from the Math and Reading & Writing (EBRW) section scores and see the national percentile rank.

Calculate the area, arc length, and chord of a circular sector from its radius and central angle — area = (θ/360)·πr², arc length = (θ/360)·2πr.

Calculate the combined capacitance of two capacitors in series using the product-over-sum rule — C = (C1 × C2) ÷ (C1 + C2).

Convert shoe sizes between EU, UK, US (Men), US (Women), and foot length in centimetres — instantly, using the documented foot-length method.

Calculate the slope (gradient) and y-intercept of the line through two points — slope = (y2 − y1) ÷ (x2 − x1) and y = mx + b.

Convert speed between metric, imperial, and nautical units — metres per second, kilometres per hour, miles per hour, feet per second, and knots.

Calculate average speed in km/h and pace in minutes per kilometre from a distance in kilometres and a time in hours.

Calculate the speed of sound in dry air from the air temperature — v = 331.3 + 0.606 × T (T in °C), about 343 m/s at 20 °C.

Calculate the volume and surface area of a sphere from its radius using V = 4/3 × π × r³ and A = 4 × π × r².

Calculate the volume, curved surface area, and base radius of a spherical cap from the sphere radius and cap height — volume = (πh²/3)(3R−h), curved surface = 2πRh, base radius = √(h(2R−h)).

Calculate the elastic potential energy (PE = ½kx²) in joules stored in a stretched or compressed spring from its spring constant and displacement.

Calculate the total square footage of a rectangular area from its length and width, with the result shown in square feet and square metres.

Find the capacity of a cylindrical, rectangular, or capsule tank in litres, US gallons, imperial gallons, and cubic metres.

Convert temperature between Celsius, Fahrenheit, and Kelvin — instantly and with exact, offset-based scale definitions.

Calculate your test grade as a percentage and a US A–F letter grade from the points you earned out of the total possible points.

Convert torque between newton-metre, pound-foot, pound-inch, kilogram-force metre, and more — instantly and with exact, newton-metre-based conversion factors.

Calculate the volume and surface area of a torus (a donut) from its major radius R and minor radius r — volume = 2π²Rr², surface area = 4π²Rr.

Calculate the secondary voltage of an ideal transformer from its turns ratio — Vs = Vp × (Ns ÷ Np), in volts (V).

Calculate the area of a trapezoid (UK: trapezium) from its two parallel sides and the perpendicular height — area = ((a + b) / 2) × h.

Calculate the area of any triangle from its base and perpendicular height using the formula area = ½ × base × height.

Calculate the output voltage of a two-resistor voltage divider — Vout = Vin × R₂ ÷ (R₁ + R₂), in volts (V).

Convert volume between metric, US customary, and UK imperial units — millilitres, centilitres, litres, cubic metres, US teaspoons, tablespoons, fluid ounces, cups, pints, quarts, US gallons, and UK gallons.

Calculate the wavelength and period of an electromagnetic wave from its frequency — wavelength = c ÷ f and period = 1 ÷ f.

Convert weight (mass) between metric and imperial units — milligrams, grams, kilograms, metric tonnes, ounces, pounds, and stone.

Estimate how many pages your word count fills for common font sizes and line spacings, with single- and double-spaced results shown clearly.

Calculate the mechanical work done by a force over a distance — work = force × distance × cos(θ), measured in joules.

Free AP Biology score calculator with 2025 score distribution. Predict your 1-5 AP exam score from MC and FRQ results instantly.

Calculate the exact number of deductible commuting days for your tax return. Automatically subtracts weekends, school holidays, and public holidays.

See how much interest and how many months you save on a car loan by adding an extra payment each month.

Calculate your exact monthly net salary as a German civil servant for any pay grade A6–A16, all 16 Bundesländer plus Bund, with real 2026 Besoldungstabellen, per-Land Familienzuschlag, the official § 32a EStG income tax formula, and PKV deduction.

Calculate your Beihilfe rate, required private health insurance (PKV) share, and your annual Kostendämpfungspauschale (deductible) in NRW.

Calculate the true financial cost of employee turnover and disengagement. Discover the precise ROI of purpose-driven alignment with our profit impact tool.

See your biweekly mortgage payment and how much interest and time you save versus a standard monthly schedule, from the loan amount, rate, and term.

Calculate the balance-weighted blended interest rate across two or three loans, plus the total balance and annual interest.

Calculate a bond's current yield from its face value, coupon rate, and market price, with the annual coupon income and any premium or discount to par.

Price a fixed-coupon bond as the present value of its coupons plus its face value, discounted at the yield to maturity, with the premium or discount to par.

Find a bond's yield to maturity — the total annual return if held to maturity — from its price, coupon, face value, and term, with the current yield alongside.

Estimate the cost of a short-term, interest-only bridge loan: the monthly interest payment, total interest, origination fee, and total cost.

Find the compound annual growth rate that takes a beginning value to an ending value over a number of years, with the total growth and the growth multiple.

See how a single deposit grows with compound interest at any frequency from annual to daily and continuous, with the interest earned and the effective annual rate (APY).

Estimate the interest-only payment during the build, total construction-phase interest, and the permanent mortgage payment for a construction-to-permanent loan.

Calculate the cost of equity with the CAPM formula from the risk-free rate, beta, and expected market return — plus the equity risk premium.

Free dimes to dollars calculator. Convert 10 dimes, 100 dimes, or any amount to dollars instantly.

Estimate a vehicle's diminished value after accident repair using the insurance industry's 17c formula.

Calculate your exact monthly liquidity gap during parental leave as a civil servant, accounting for capped Elterngeld and continued private health insurance.

Calculate trip fuel cost and split by passenger. Supports l/100km, mpg US, mpg UK, and km/l.