About Reckoner

The name

A ready reckoner is a printed table of computed values, sold so that nobody has to do the arithmetic again. That is what this site is and it is where the name comes from. You are not meant to work anything out here. You are meant to leave with the sheet that has the answers already set on it.

How the figures are made

Every table is computed in your own browser at the moment you ask for it. Nothing is uploaded and nothing is stored, and no file here is a scan or a copy of anyone else’s sheet.

Every figure that reaches a sheet is computed twice, by two routes that share no working. One route sets the table and then reads back the numerals it actually drew. The other works the same figures out again from the range and the rule alone. A figure is printed only where both routes agree, and where they disagree nothing is printed. The counts quoted on the pages of this site are held to the same rule: 144 cells, 59 distinct products, 25 shaded primes are all figures that survived being computed twice.

What is not set

The press refuses tables it could set exactly but nobody could read. A multiplication chart to 50 would be 2,500 products at 4.55 points, so it is not offered and there is no page for it. Where a table you went looking for is missing from this site, that is usually the reason.