Math & Life

2 tools - Percent, units, currency and timers.

About the category

The Math & Life category is a collection of everyday calculators: percentages, discounts, unit conversions, currency, dates, time, finance, and random number utilities. It is the category you open when you need a quick, accurate number - no spreadsheet, no calculator app, no mental math.

How to choose a tool

If you need to calculate a discount, tip, or markup

Use the Percentage Calculator. It handles all four common percentage questions with clear labels.

If you need to convert between units

Use the Unit Converter. Pick your category (weight, length, temperature), then from/to units - incompatible categories are automatically hidden.

If you need to compare two values over time

Use the Percentage Calculator's 'percentage change' mode to see how much something increased or decreased.

Frequently Asked Questions

Why does 1 kg show as 2.204623 pounds, not 2.2? v

Because 1 kg = 2.20462262... pounds exactly. The rounded 2.2 is fine for everyday estimates but drifts 0.2% per kg. OmniTools uses the exact factor so you can trust the precision.

Why is temperature conversion different from other units? v

Because temperature has an offset, not just a scale. 0 C is not 0 F - the freezing points differ by 32 degrees. The formula is: F = C x 9/5 + 32.

How do I calculate a 15% tip on $45? v

Use the Percentage Calculator: 'What is X% of Y' mode. X = 15, Y = 45. The answer is $6.75. Add to your bill for a total of $51.75.

Can I convert currencies here? v

No. Currency rates change daily, so we'd need live data. This category covers fixed physical units (weight, length, temperature) with constant conversion factors.

What does 'swap' do in the unit converter? v

It swaps From and To. If you had kg to lb, after swap you have lb to kg, showing the reverse conversion.

Are the calculations exact? v

For unit conversion, yes - we use international standard factors. For percentages and float math, results are accurate to 15 significant digits, which is more than enough for currency, science, and everyday use.

Enjoying OmniTools? This site stays free thanks to ads. Please consider whitelisting us in your ad blocker. Thank you!