Number List Tools: Sum, Round, Filter, Analyse

1. Choose an Operation. Sum is selected to start; each operation also has its own address, such as /add-integers or /round-a-number, that opens the page with it chosen.
2. Pick how the numbers are separated: new line, comma, space or a custom text such as a semicolon. Blank items and spaces around each number are ignored.
3. Type or paste the numbers. A note such as "12 numbers read." confirms how many were understood, and an item that is not a number is named with its position.
4. Adjust the options that appear for the chosen operation, such as the number of decimal places or the comparison value.
5. Copy the result or download it as a text file. Lists of results are written with the same separator as the input.

Sum adds every number and Product multiplies them. Running total writes the sum of the first one, two, three and more numbers, so 1, 2, 3, 4 becomes 1, 3, 6, 10, and Running product does the same with multiplication. Because a product can grow very quickly, results longer than 100,000 digits are refused with a message rather than freezing the page.

Round to tens or significant digits rounds each number to the nearest 10, 100, 1,000 and so on, or to a chosen number of significant digits, with halves rounded away from zero: 1250 to the nearest 100 is 1300. Round to decimal places keeps a fixed number of places and offers six rounding modes. Half up rounds halves away from zero, half even (banker's rounding) rounds them to the even neighbour, up and down mean away from and towards zero, and ceiling and floor mean towards positive and negative infinity. Truncate either drops the last k digits of the whole part, so 12345 without its last two digits is 123, or cuts decimals to a number of places towards zero.

Increment and Decrement add or subtract a step, which may itself be a decimal or negative. Enumerate puts a position in front of each number, starting from 1 or any other whole number, followed by a text such as ". ". Join writes the whole list on one line with a glue of your choice, which is handy for turning a column of numbers into a comma-separated value list.

Extract numbers from text reads any text, such as a log, an email or a table copied from a web page, and lists the numbers in it. Integers takes every run of digits; every number also keeps decimal points and a minus sign, but only when the sign does not follow a letter or a digit, so a date like 2024-05-01 gives three positive numbers. Even integers and Odd integers keep whole numbers of that parity; a decimal such as 2.5 is neither. Filter by comparison keeps numbers that are greater than, at least, less than, at most, equal to or not equal to a value, lie between two values inclusive, are divisible by a whole number, or are prime.

Analyse integers writes one line per integer saying whether it is even or odd, prime, a perfect square and a perfect cube, how many digits it has, its digit sum, and whether it is divisible by 3, 5 and 9. Rewrite as a sum splits each whole number into a chosen number of parts that are as equal as possible (10 into 3 parts is 4 + 3 + 3), into random positive parts that you can draw again, or into the powers of two that make up its binary form (13 is 8 + 4 + 1).