# Calculator Porch

> Free online calculators for math, statistics, money, construction, solar energy, pets and everyday life, each with its formula, steps and cited sources.

Every calculator shows its formula, a worked example and its sources; calculations run in the browser and nothing typed is stored.

## Math

- [Math calculators](https://calculatorporch.com/math/): Free math calculators that show the formula and a worked example: Fraction Calculator.
- [Fraction Calculator](https://calculatorporch.com/math/fraction-calculator/): Free fraction calculator: add, subtract, multiply and divide fractions and mixed numbers, with every step shown and the answer in simplest form.

## Statistics

- [Statistics calculators](https://calculatorporch.com/statistics/): Free statistics calculators that show the formula and a worked example: Random Number Generator and Standard Deviation Calculator.
- [Random Number Generator](https://calculatorporch.com/statistics/random-number-generator/): Random number generator for any range: pick one or many numbers, with or without repeats, using cryptographic randomness so each is equally likely.
- [Standard Deviation Calculator](https://calculatorporch.com/statistics/standard-deviation-calculator/): Standard deviation calculator with every step of the calculation shown: the standard deviation, variance and mean of a sample or a population.

## Everyday Life

- [Everyday Life calculators](https://calculatorporch.com/everyday-life/): Free everyday calculators that show the formula and a worked example: Day Counter and Age Calculator.
- [Day Counter](https://calculatorporch.com/everyday-life/day-counter/): Day counter: count the days between two dates, with or without the end date, in days, weeks, weekdays and weekend days. Leap years handled.
- [Age Calculator](https://calculatorporch.com/everyday-life/age-calculator/): Age calculator: your exact age in years, months and days from your date of birth, today or on any date, plus weeks, days, next birthday and milestones.

## Construction

- [Construction calculators](https://calculatorporch.com/construction/): Free construction calculators that show the formula and a worked example: Gravel Calculator and Square Footage Calculator.
- [Square Footage Calculator](https://calculatorporch.com/construction/square-footage-calculator/): Square footage calculator: find square feet for rectangles, circles and triangles, convert to square yards, square meters and acres, and estimate cost.
- [Gravel Calculator](https://calculatorporch.com/construction/gravel-calculator/): Gravel calculator and driveway gravel estimator: how much gravel you need in cubic yards, tons and bags, by gravel type and depth, with a cost estimate.

## Finance

- [Finance calculators](https://calculatorporch.com/finance/): Free finance calculators that show the formula and a worked example, including the Gold Calculator, 3D Printing Cost Calculator and Tip Calculator.
- [Percent Off and Percentage Calculator](https://calculatorporch.com/finance/percent-off-calculator/): Percent off and percentage calculator: sale price and savings at any discount, P% of a number, what percent X is of Y, and percentage change or difference.
- [Tip Calculator](https://calculatorporch.com/finance/tip-calculator/): Tip calculator and gratuity calculator: work out the tip and total for any bill, split it between people and round each share up to a whole dollar.
- [3D Printing Cost Calculator](https://calculatorporch.com/finance/3d-printing-cost-calculator/): 3D printing cost calculator: what a print really costs (filament, power, wear, failed prints, your time) and a price that keeps your margin after fees.
- [Gold Calculator](https://calculatorporch.com/finance/gold-calculator/): Gold calculator: enter today's rate and value gold in tola, masha, ratti, grams or ounces at any karat, with making charges, tax and resale deductions.

## Energy & Solar

- [Energy & Solar calculators](https://calculatorporch.com/energy/): Free energy calculators that show the formula and a worked example: Solar Panel Calculator.
- [Solar Panel Calculator](https://calculatorporch.com/energy/solar-panel-calculator/): Solar panel calculator for any country: system size and panel count from the units (kWh) on your bill, with NASA sun hours for 197 cities worldwide.

## Pets

- [Pets calculators](https://calculatorporch.com/pets/): Free pet calculators that show the formula and a worked example: Dog Pregnancy Calculator.
- [Dog Pregnancy Calculator](https://calculatorporch.com/pets/dog-pregnancy-calculator/): Dog pregnancy calculator: estimate the due date and whelping window from the mating, ovulation or LH-surge date, with a week-by-week calendar.

## Optional

- [10 Days From Today](https://calculatorporch.com/everyday-life/day-counter/10-days-from-today/): Find the date 10 days from today, the day of the week, and 10 business days from today, with a table for each upcoming start date.
- [2/3 times 2/3 in fraction form](https://calculatorporch.com/math/fraction-calculator/2-3-times-2-3/): 2/3 times 2/3 in fraction form is 4/9. See the step-by-step working, the decimal (0.4444) and similar problems.
- [2 1/3 minus 2/3 as a fraction](https://calculatorporch.com/math/fraction-calculator/2-1-3-minus-2-3/): 2 1/3 minus 2/3 as a fraction is 5/3 (1 2/3). See the step-by-step working, the decimal (1.6667) and similar problems.
- [2/3 in Fraction Form](https://calculatorporch.com/math/fraction-calculator/2-3-in-fraction-form/): 2/3 is already a fraction in simplest form. See it as a decimal (0.6667) and a percent, plus its equivalent fractions.
- [3 1/3 divided by 4](https://calculatorporch.com/math/fraction-calculator/3-1-3-divided-by-4/): 3 1/3 ÷ 4 = 5/6. See the step-by-step working, the decimal (0.8333) and similar fraction problems.
- [2 1/3 times 2](https://calculatorporch.com/math/fraction-calculator/2-1-3-times-2/): 2 1/3 × 2 = 14/3 (4 2/3). See the step-by-step working, the decimal (4.6667) and similar fraction problems.
- [1 1/2 times 1/4](https://calculatorporch.com/math/fraction-calculator/1-1-2-times-1-4/): 1 1/2 × 1/4 = 3/8. See the step-by-step working, the decimal (0.3750) and similar fraction problems.
- [Random Number Generator 1 to 16](https://calculatorporch.com/statistics/random-number-generator/1-to-16/): Random number generator for 1 to 16: pick one number or several, with or without repeats. Each has a 1 in 16 chance; see the odds of repeats.
- [40% Off $60](https://calculatorporch.com/finance/percent-off-calculator/40-percent-off-60/): 40% off $60 is $36.00: you save $24.00. See the working, other discounts on $60, and 40% off other prices.
- [All calculators A–Z](https://calculatorporch.com/calculators/)
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- [Contact](https://calculatorporch.com/contact/)
- [About the author, Ahsan Khan](https://calculatorporch.com/authors/ahsan-khan/)
- [Full text for LLMs](https://calculatorporch.com/llms-full.txt)