Bulk Buy and Order Quantity Calculator

Ten per cent off if you take twelve hundred. On these figures that saves two thousand one hundred and sixty dollars and costs one thousand two hundred and fifteen to hold. It nets nine hundred and forty-five, so it is a good deal.

Take twenty-two hundred of the same thing at the same discount and it loses money.

The reason is that the two halves of the sum do not grow at the same speed. The saving is linear: buy twice as many, save twice as much. The holding cost is not, because buying twice as many means holding twice as much for twice as long — so it goes up four times. Somewhere in the middle there is a best quantity, and it is almost always smaller than the one being offered.

So the page puts the discount and the cost of holding on the same scale, as rates, where they can be compared directly. Ten per cent saved against six and a quarter per cent spent holding it is a deal. Ten per cent against fourteen is not, and it looks identical on the invoice.

It finds the quantity that nets most, and the quantity above which the whole thing turns negative, and shows the range around them so you can see how flat or sharp the peak is.

It counts what goes out of date. Anything still sitting there past the point where you can sell it is a write-off, not stock, and two years of cover on an eighteen month product means a quarter of it was never going to sell.

The holding rate is your figure and the answer moves with it. It covers storage, insurance, damage, and what the money would have earned elsewhere — twenty to thirty per cent a year is the usual working range for a small business, but if you own your warehouse outright and the cash would otherwise sit in a current account, yours is lower. The page will not pretend to know which.

It does not forecast the price. Whether this offer comes round again, and whether the unit cost is heading up or down, are questions about the future that no arithmetic here can answer. If you have a real reason to think the price is about to rise, that is a reason this page cannot see, and it belongs in the decision alongside the number rather than inside it.

Save as many versions as you like and put any two side by side, figure against figure, with the better one on each line marked and the difference in its own column. That screen is the one that decides things, and it is the part a free calculator cannot do at all. The same discount is a good deal on a fast line and a bad one on a slow line, and the only difference is how long you sit on it.

One HTML file. No account, no subscription, no internet needed. Opens on Windows, Mac and Android; the readme explains the extra step on iPhone and iPad, where Apple blocks JavaScript in downloaded files and every tool of this kind is affected.

Everything lives in your browser on your device. Nothing is uploaded, which is why it works offline and why nobody else can see your figures — and it also means clearing your browsing data deletes it. The tool does not pretend otherwise: the header shows how long since your last export at all times, turns amber after three days and red after seven, and export is one click that produces a plain file you keep.