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Tool Collection
Everyday Calculator Tools
This topic groups common calculation, measurement and random-value pages for quick everyday number work.
3 tools3 related articles
How To Use This Collection
Use the task notes to define the workflow first, then move into the tool pages below in the order that fits the job.
- Check discounts or percentage changes
- Convert measurement units quickly
- Generate random values without opening a spreadsheet
Related Articles
These articles explain the technical topics and processing boundaries behind related tools.
Unit Conversion: Exact Definitions and Where Conversions Go Wrong
An inch is exactly 25.4 mm and a pound is exactly 0.45359237 kg. Which conversions are exact, which are not, and why temperature and fuel economy behave differently.
Percentage Change: The Formula and Four Ways It MisleadsHow to compute percent change correctly, why percent and percentage points are different, and why a 50% drop needs a 100% rise to recover.
Exchange Rates for Pricing: Spot, Mid-market and the Spread You Actually PayThe rate on a news site is not the rate on an invoice. How mid-market, bid and ask differ, and how to avoid silent margin errors.
Tools In This Collection
Start from these tools, then move back into articles and adjacent collections as the workflow expands.
Calculator
Percentage Calculator
Calculate percent of, percent ratio, increase/decrease, and add/subtract percentage.
percentage-calculator
Calculator
Unit Converter
Convert length, mass, temperature, area, volume and speed with bidirectional inputs.
unit-converter
Utility
Random Number Generator
Generate random integers or decimals with range, quantity, uniqueness and sorting options.
random-number-generator