Long addition is the column method every American third-grader learns and every adult quietly still uses. Stack the numbers so the ones, tens, and hundreds line up, add each column starting from the right, and carry any ten-or-more into the next column. Adding 4,857 and 2,968: the ones column gives 15, so you write 5 and carry 1; the tens column gives 15 again, write 5, carry 1 — and the final total lands at 7,825. The carrying is the whole trick, and it never changes no matter how many digits you stack.

Receipts, invoices, and score sheets are where adults meet it: totaling six grocery receipts, summing a season of bowling scores, or checking a restaurant bill split six ways. This tool adds up to six numbers at once and shows both the total and the average, which covers the two questions people actually ask — "what is the sum?" and "what is typical?" Type each value in its own numbered field and the Total Sum and Average appear instantly, no column alignment or carried digits required.

With the pre-filled defaults — Number 1 1,234, Number 2 5,678, Number 3 910, Number 4 0, Number 5 0, Number 6 0 — the Long Addition Calculator returns Total Sum 7,822, Average 1,303.67. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.