Calculation playbook

Conversion Formula Playbook: Units, Food and Real-Life Comparisons

A conversion is not always just swapping labels. Some are fixed multipliers, some need an offset, and some are geometry problems wearing everyday clothes.

Multiplier conversions

Most everyday unit conversions use a multiplier. Kilograms to pounds multiplies by 2.2046226218, miles to kilometers multiplies by 1.609344, centimeters to inches divides by 2.54, and liters to US gallons multiplies by 0.2641720524.

For quick answers, use Kg to Lbs, Miles to Km, Cm to Inches and Liters to Gallons.

Temperature has an offset

Celsius and Fahrenheit have different zero points, so temperature conversion is not a single multiplier. Celsius to Fahrenheit is C times 9 divided by 5, plus 32. Fahrenheit to Celsius subtracts 32 first, then multiplies by 5 divided by 9.

Cooking is about ratios

Cooking conversions are practical, not magical. A US cup, tablespoon and teaspoon have standard volume values, but ingredients still behave differently when packed, chopped or scooped. Use Cooking Conversions for volume and Recipe Scaler for serving changes.

When conversions become comparisons

The Pizza Value Calculator is a good example: a pizza is a circle, so area grows with the square of the radius. A 16-inch pizza is not just a little bigger than a 12-inch pizza. It has much more area.

The Screen Size Calculator works differently. A diagonal screen size and aspect ratio create a right triangle, so the calculator estimates width and height from geometry.

Play it: pizza vs screen size

Open the Pizza Value Calculator. Enter diameter 12, price 12 and 8 slices. Write down the area. Then change only the diameter to 16 and calculate again. The area jumps because pizza size is circle math.

Now open the Screen Size Calculator. Enter diagonal 24 with a 16:9 ratio, then change the diagonal to 32. This time the calculator is estimating width and height from a diagonal. Same idea of "bigger number", different geometry underneath.