# Calculator Friendly

> Free, accurate, mobile-friendly online calculators for finance, health, dates, construction and conversions — each tool crafted carefully with clear instructions, transparent formulas and ad-light pages.

Calculator Friendly publishes hand-built calculators and in-depth explainer articles. Every calculator page includes a "How to use" guide, the underlying formula, worked examples and a long-form article so AI assistants and readers can cite accurate, sourced information.

## Calculators

### Finance

- [Retirement Savings Calculator](https://calculatorfriendly.com/calculators/retirement-savings-calculator): How long will your retirement savings last? Compare two scenarios with starting balance, rate of return, annual income and inflation — see the year-by-year withdrawal schedule.
- [Money Market Account Calculator](https://calculatorfriendly.com/calculators/money-market-account-calculator): Project the future value of a money market account from your starting balance, recurring deposit, APY and term — see total contributions, interest earned and a year-by-year growth schedule.
- [USA eBay Fees Calculator](https://calculatorfriendly.com/calculators/usa-ebay-fees-calculator): Estimate eBay.com final value fees, payment processing, promoted listings, store discounts and sales tax — see your seller payout and profit per order with a category-by-category fee breakdown.
- [GM Income Calculator](https://calculatorfriendly.com/calculators/gm-income-calculator): Convert any pay rate into your gross monthly (GM) income — hourly, daily, weekly, biweekly or annual. Adjustable hours per day and days per week, with a full pay-frequency breakdown.

### Health

- [Water Intake Calculator](https://calculatorfriendly.com/calculators/water-intake-calculator): Estimate your recommended daily water intake based on body weight, activity level, climate and optional creatine intake — get a personalised hydration target in liters and ounces.
- [Pool Salt Calculator](https://calculatorfriendly.com/calculators/pool-salt-calculator): Find out how much pool salt to add (or how much water to replace) to reach the ideal 3,200 ppm salinity for your saltwater pool — supports US gallons, UK gallons, liters and cubic meters.
- [Arterial Blood Gas (ABG) Calculator](https://calculatorfriendly.com/calculators/arterial-blood-gas-calculator): Interpret arterial blood gas results from pH, PaCO₂ and HCO₃⁻ — identifies the primary acid-base disorder, expected compensation (Winter's formula), and anion gap with delta-delta when sodium and chloride are provided.

### Date & Time

- [How Many Days Till Calculator](https://calculatorfriendly.com/calculators/how-many-days-till): Count the exact days, weeks, months and years between two dates — or add/subtract time from any date. Optional business-day mode with US holidays.
- [How Many Hours in a Month Calculator](https://calculatorfriendly.com/calculators/hours-in-a-month-calculator): Find out how many hours are in a month — for the average month, any specific calendar month or a 30-day month. Convert hours to months and months to hours with a precision toggle and a working-hours mode.

### Construction

- [Square Foot Calculator](https://calculatorfriendly.com/calculators/square-foot-calculator): Calculate the square footage of rectangles, circles, triangles, trapezoids, sectors and more — with unit conversion, quantity and optional cost.
- [Bitumen Calculator](https://calculatorfriendly.com/calculators/bitumen-calculator): Estimate asphalt mix volume, total tonnage, bitumen binder and aggregate quantities for a pavement layer — with optional cost per tonne and metric/imperial units.
- [Cinder / Concrete Block Calculator](https://calculatorfriendly.com/calculators/concrete-block-calculator): Estimate how many concrete blocks (CMUs), bags of mortar and total dollars you need for any wall — preset US block sizes or custom dimensions, with metric & imperial units and a waste %.
- [Paver Calculator](https://calculatorfriendly.com/calculators/paver-calculator): Estimate how many patio pavers you need, project area and total cost (pavers + installation) — preset US paver sizes or custom dimensions, with metric & imperial units and a waste %.

### Conversion

- [Ounces to Cups Calculator](https://calculatorfriendly.com/calculators/ounces-to-cups-calculator): Convert fluid ounces to cups (and back) across US legal, US customary, metric, UK and Japanese cup sizes — with US and UK fluid ounce support and an instant conversion chart.
- [Ounces to Pints Calculator](https://calculatorfriendly.com/calculators/ounces-to-pints-calculator): Convert ounces to pints (and back) for fluid ounces or weight ounces — supports US liquid, US dry and UK imperial pints, with built-in densities for common cooking ingredients.
- [Ounces to Gallons Calculator](https://calculatorfriendly.com/calculators/ounces-to-gallons-calculator): Convert ounces to gallons (and gallons back to ounces) for fluid ounces or weight ounces — supports US and UK gallons, with built-in densities for common cooking ingredients.
- [Ounces to Grams Calculator](https://calculatorfriendly.com/calculators/ounces-to-grams-calculator): Convert ounces to grams (and grams back to ounces) for both avoirdupois and troy ounces — instant results with a precision toggle and a quick-reference oz to g chart.
- [Ounces to Kilograms Calculator](https://calculatorfriendly.com/calculators/ounces-to-kilograms-calculator): Convert ounces to kilograms (and kg back to oz) for both avoirdupois and troy ounces — instant results, decimal precision toggle and a quick-reference oz to kg chart.

## Site pages

- [Home](https://calculatorfriendly.com/): Overview of all calculators by category.
- [Sitemap](https://calculatorfriendly.com/sitemap): Full searchable index of every calculator.
- [About](https://calculatorfriendly.com/about): Who builds Calculator Friendly and why.
- [Editorial policy](https://calculatorfriendly.com/editorial-policy): How calculators and articles are researched, written and reviewed.
- [Contact](https://calculatorfriendly.com/contact): Get in touch with the team.

## Optional

- [Privacy policy](https://calculatorfriendly.com/privacy)
- [Terms](https://calculatorfriendly.com/terms)
- [Disclaimer](https://calculatorfriendly.com/disclaimer)
- [Cookies](https://calculatorfriendly.com/cookies)