Math
Significant figures, scientific notation, dimensional analysis, printable graph paper, function graphing, and a visual explanation of eigenvectors and PCA.
This section covers the quantitative housekeeping that every science and statistics problem depends on: counting significant figures correctly, converting to and from scientific notation, and carrying units through a calculation so a dimensional mistake shows up before the answer does. The same care extends to the everyday conversions that trip people up: moving a pressure across eleven units at once on exact NIST factors, reducing a ratio to lowest terms with the GCD shown, or spelling a number into words with its short-scale and hyphenation rules stated up front rather than assumed. Every conversion shows the exact factor and rule it used, so the arithmetic underneath a science or statistics problem holds up to inspection.
It also produces printable graph paper and practice worksheets when you need to work a problem on paper. Use the function grapher to plot up to five real-valued functions, restrict their domains, and export a clean SVG without hiding gaps or asymptotes.
The section also covers the objects that arithmetic acts on. Use the eigenvectors and PCA page to rotate a line through a cloud of points until the spread along it is greatest, watch the perpendicular error fall by the same amount, and see that the direction you settled on is the top eigenvector of the covariance matrix. Every figure there is one you operate, and each step shows the numbers behind it, the same standard the converters hold to.
Units, Notation, and Precision
Convert between units, write a number in the form the work calls for, and carry the right number of digits through a calculation.
Sig Fig Calculator
Count and round significant figures from the typed number, including decimal zeros, exact numbers, and scientific notation.
Scientific Notation Converter
Convert decimal, scientific, and E notation while preserving reported trailing zeros and showing engineering notation.
Dimensional Analysis Calculator
Convert units with a factor-label trace, exact conversion-factor notes, and dimension mismatch checks.
Pressure Unit Converter
Convert a pressure across eleven units at once, with exact NIST factors.
Ratio Simplifier: Reduce Any Ratio to Lowest Terms
Reduce any ratio to lowest terms by GCD, including three-term ratios, decimals, fractions, negatives, and terms in different units.
Number to Words Converter: Spell Out Any Number in English
Spell any number out in English words with short scale, hyphenation, American or British "and", decimals, negatives, ordinals, and US check writing named on the page. Reverse parser included.
Graphing and Printable Practice
Plot functions with honest gaps, or generate calibrated graph paper and drill worksheets for work away from the screen.
Printable Graph Paper
Generate printable square, dot, isometric, polar, and coordinate-plane graph paper with physical spacing and calibration bars.
Free Math Worksheets: Printable Drills with Answer Key
Generate reproducible printable arithmetic drill worksheets with answer keys, seeds, and print calibration.
Function Grapher
Plot up to five real-valued functions, inspect how each expression was parsed, and export a clean graph in your browser.
Linear Algebra and Structure
Interactive explanations of vectors, matrices, eigenvectors, and the structures they reveal.