How Much Water Do You Need? Guidelines and a Simple Estimate
There is no single right amount of water. Here is what official intake guidelines say, how to estimate a range from body weight, and when needs go up.
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Plain-English guides to the numbers in everyday life: how a calculation works, where people go wrong, and which tool to reach for.
How Overtime Pay Is Calculated: Time-and-a-Half Worked Through
Overtime math is simple once you know the regular rate and the threshold. Follow worked examples for hourly, bonus and salaried pay.
How Ratios Work: Simplifying, Comparing and Sharing
A ratio compares two or more quantities. Learn to simplify one, tell part-to-part from part-to-whole, and share a total in a given ratio.
How Roman Numerals Work: Rules and Easy Conversion
Roman numerals follow a handful of rules. Learn the symbols, the six subtractive pairs and a place-by-place method that converts any year or number in seconds.
How Sales Commission Works: Flat, Tiered and Marginal Rates
The same sales can pay very different commission depending on how the tiers are applied. This guide compares the three common structures with numbers.
How to Calculate a Break-Even Point in Units and Revenue
Your break-even point is the sales level where income equals costs. Here is the hand calculation in units and in revenue, plus how a price change moves it.
How to Calculate a Monthly Loan Payment by Hand
A loan payment comes from one short formula. Work through it with real numbers, see how term and rate change the total cost, and learn to check a lender's quote.
How to Calculate Age From a Date of Birth by Hand
Subtracting years is only half the job. Here is the borrow method for an exact age, a way to check it in days, and what happens to 29 February birthdays.
How to Calculate BMI by Hand in Metric and Imperial Units
BMI is one division and one squared number. Here is the metric and imperial method, the common unit slips, and how to run the formula backwards to find a target weight.
How to Calculate CAGR by Hand, Step by Step
CAGR turns a start value, an end value and a time span into one smoothed yearly rate. Here is the formula, a full calculation and the traps to avoid.
How to Calculate Hours Between Two Times, Even Overnight
Time subtraction trips people up because minutes run to 60 and a shift can cross midnight. Here is a reliable method, with a break deducted and a flight example.
How to Calculate How Many Tiles You Need for a Floor or Wall
Dividing room area by tile area gives a minimum, not an order. Counting rows and columns, then adding waste, gives a number you can actually buy.