Popular Calculators

Business & Ecommerce

Return on Equity Calculator

Calculate return on equity (ROE) using net income and average shareholder equity. Measure how effectively a business generates profit from owners' equity.

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Business & Ecommerce

Return on Invested Capital Calculator

Calculate return on invested capital (ROIC) using EBIT, tax rate, and invested capital. Measure how efficiently a business generates returns from capital.

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Business & Ecommerce

Revenue Per Employee Calculator

Calculate revenue per employee from total revenue and employee count. Compare RPE with a target and estimate revenue efficiency and staffing productivity.

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Business & Ecommerce

Revenue Per Visitor Calculator

Calculate revenue per visitor from total revenue and website visitors. Compare RPV with a target and estimate conversion rate, AOV, and target revenue.

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Real Estate and Lending

Reverse Mortgage Calculator

Estimate reverse mortgage proceeds, principal limit, upfront costs, monthly advances, projected loan balance, home value, and remaining equity.

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Physics & Engineering

Reynolds Number Calculator

Calculate Reynolds number, velocity, pipe diameter, or viscosity and identify laminar, transitional, or turbulent fluid flow.

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Math & Geometry

Rhombus Calculator

Calculate rhombus area, perimeter, diagonals, and side length quickly with this accurate and easy-to-use rhombus calculator.

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Math & Geometry

Right Triangle Calculator

Use our Right Triangle Calculator to find missing sides, angles, area, and perimeter of a right triangle with accurate results instantly.

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Everyday Life

Ring Size Converter

Use our free Ring Size Converter to convert US, UK, EU and Japan ring sizes instantly, with diameter and circumference measurements in millimeters.

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Investment and Trading Calculators

Risk-Reward Ratio Calculator

Calculate trading risk, potential reward, risk-reward ratio, break-even win rate, and position size for long or short trades instantly.

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Construction and Home

river rock calculator

Calculate river rock in cubic yards, tons, pounds, and bags using area, depth, density, waste percentage, and optional material cost.

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Electrical & Solar

RLC Circuit Calculator

Calculate RLC circuit impedance, reactance, phase angle and resonance frequency instantly using resistance, inductance, capacitance and frequency.

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Marketing Calculators

ROAS Calculator

Use our free ROAS Calculator to measure return on ad spend, revenue efficiency, break-even ROAS, profit, and advertising performance instantly.

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Finance

ROI Calculator

Use this ROI Calculator to measure return on investment, profit, gain, cost, and ROI percentage quickly with a clean professional tool.

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Math

Roman Numeral Converter

Convert numbers to Roman numerals or Roman numerals to numbers instantly. Free, accurate, mobile-friendly tool with examples, rules, and FAQs.

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Construction

Roof Area Calculator

Use this free Roof Area Calculator to estimate the surface area of gable and shed roofs from building dimensions, roof pitch, and overhangs. Calculate sloped roof area, plan area, roof angle, slope multiplier, rafter slope length, and roofing squares instantly.

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Construction

Roof Pitch Calculator

Use this free Roof Pitch Calculator to convert rise and run into roof pitch, slope percentage, roof angle, pitch ratio, and rafter length. Supports common measurement units and instant calculations.

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Construction

Roof Shingle Calculator

Calculate roof shingles, bundles, roofing squares, waste allowance and estimated material cost from your roof area with this free calculator.

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Construction and Home

Roofing Calculator

Free roofing calculator to estimate shingles, squares, and material costs by roof size, pitch, and type. Get instant, accurate estimates online.

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Advanced Finance and Investment

Roth IRA Calculator

Thousands of free online calculators and converters for math, finance, health, science, and everyday life. Fast, accurate, and always free.

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Math & Geometry

Rounding Calculator

Round numbers to the nearest whole number, tenth, hundredth, or thousandth. Get accurate results with clear rounding steps and an easy-to-use calculator.

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Vehicle and Practical Calculators

rpm to mph

Convert RPM to MPH using tire size, gear ratio and final drive. Fast, free RPM speed calculator for cars, bikes and custom builds.

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SaaS

Rule of 40 Calculator

Calculate your SaaS Rule of 40 score by combining revenue growth and profit margin to evaluate business growth and profitability.

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Finance

Rule of 72 Calculator

Use our Rule of 72 Calculator to estimate how long an investment takes to double or the annual return needed to reach your financial goal.

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