Why most words-to-pages tools are wrong for newspapers
Type a word count into a general purpose estimator and it will assume a sheet of A4, one column, twelve point double spaced. That describes an essay. It describes nothing at all about a newspaper, which sets nine point type in five narrow columns on a sheet that is nearly four times the area. The gap between the two is not a rounding error, it is a factor of five or more, and planning a print run on the wrong one wastes real money.
So this estimator does not carry a stored words-per-page figure. It builds one from the page you actually chose. The printable width comes from the printer's own trim size and margin. Subtract the gutters between columns and divide by the number of columns to get a column width. The body size gives a line height at 1.2 times the point size, and an average character width of about half the point size, which is a reasonable figure for a serif text face at newspaper sizes. Column width divided by character width gives characters per line. Divide by 5.1, the average length of an English word with its trailing space, and you have words per line. Multiply by the number of lines that fit in the column height, then by the number of columns.
Every one of those steps is printed in the table below the calculator. If you think 5.1 characters is wrong for your writing, or that your typeface is narrower than average, you can see exactly where that assumption enters and judge the answer accordingly. A number you can argue with is more useful than one you have to trust.
The slider is the most important control
A page of unbroken body text almost never exists outside a classified section. Real pages carry headlines, standfirsts, photographs, captions, bylines, pull quotes and white space, and together those take a large share of the paper. The slider is where you tell the estimator how much.
A third is a sensible default for a text led feature page. A news page with several photographs runs closer to forty-five percent. A picture led spread can reach two thirds, and a page that is essentially one large image with a caption is higher still. If you are unsure, look at a newspaper you like and estimate by eye. Being roughly right here matters far more than being precise about character widths.
Body size moves the answer more than you expect
Going from nine point to ten point looks like an eleven percent change. It is not. Type scales in both directions at once: every line gets taller and every character gets wider, so you lose capacity vertically and horizontally at the same time. The compound effect is closer to a fifth of the page, which is why newspapers set body copy so small and why a well meaning decision to make everything more readable can add four pages to a print bill.
Columns work the other way and are worth experimenting with. Narrower columns fit more words into the same paper, because a shorter line wastes less space at the end of each one. There is a limit: below about thirty characters a line the text starts to hyphenate badly and read poorly, which is roughly where newspapers stop.
What the second number is for
The estimator reports the pages your text fills and, next to it, the number you would actually order. Those are rarely the same, because presses work in folded sheets and page counts come in multiples of four, or two on Newspaper Club's traditional broadsheet. Text that fills thirteen pages means ordering sixteen.
Treat the difference as planning information rather than an annoyance. Three spare pages is a back cover, a picture page and a contributors list, and deciding that while you still have time is far better than filling them in a panic. If the count exceeds what the format allows at all, the calculator says so, and the answer is either a larger format or a shorter paper.