So far, I have discovered one good book focused solely on England’s medieval wine trade. Margery Kirkbride James’s research on the trade was collected into an edited collection entitled Studies in the Medieval Wine Trade by scholar E. M. Carus-Wilson.

Unfortunately, the scholar who generated most of the interesting content succumbed to a health issue before she could complete her scholarly project of a comprehensive book on the trade.

But the finished work is interesting and detailed enough that a writer could easily construct a story around, say, a wine trader or the ship master of a small caravel.

The ship master, either a hired captain or a full or partial owner of the ship, might command a vessel with 30 tons of cargo capacity. Remember that the weight of the crew, provisions, equipment, weapons, armor, and other supplies reduce the overall amount of additional cargo.

For the hardcore worldbuilders, have fun sorting out the differences between “u” and “o” and all other issues related to weights, measures, and currency valuations. Accept some imprecision in your pursuit of realism, or medieval reality will drive you insane. Numerical precision in medieval times is a functional oxymoron.

But if you use some variant of a pound-shilling-pence system (I call my money units the crown, shenar, and the penny in my fiction) and do some math, you can calculate reasonable margins and profits.

Wine typically shipped in tun barrels of 252 gallons (or 2 pipes). Your ship master’s small ship might carry about 25 to 27 tuns.

According to James, a customs duty of 2s per tun was a common assessment. The crown’s reserved purchase share was often 1 tun for ships carrying 10 to 19 tuns or 2 tuns from cargos 20 tons and up. The set wholesale price for the crown was 20s per tun, or about 1d per gallon (or a bit less). So far as I can tell, you could charge about two to five times that amount to a regular buyer, depending on the quality of the wine and other trade variables. A tun of wine, in other words, might sell wholesale to a non-royal buyer for 3 to 5 pounds, and those gallons at retail prices might earn upwards of 4 to 9 or 10 pounds.

But what about your taxes and operating expenses?

These wine-filled tun barrels or casks were no joke in terms of size—think of each one as something like 4 by 5 feet and somewhere around 2,000 pounds of weight.

The port or river balletage, an entry tax, was often 2d per tun.

Loading or unloading the tuns typically would cost about 2d each.

You could stow your wine in a nearby warehouse for a fee of 4d per day, with anywhere from 1 to 4 d per tun of additional charges for supports.

A prudent trader would hire some boys to watch their cargo and raise the hue and cry if thieves went for it. The boys would cost 2d per day and 3d per night.

Hiring a carter to carry the merchandise to a particular nearby cellar cost 3d per tun. For longer journeys, a half pence per gallon per day for trips under thirty miles or 1d per gallon per day for trips over 50 miles fit with the records James found. Her calculations indicate that freight charges from 6s to 13s per tun were normal, with traders leaning on sea and river transport as much as possible.

The retail price for the wine at the vendor point of sale might range from 4d per gallon up to 9d per gallon, and sometimes higher, depending on the wine’s quality or the seller’s proximity to a dock. So buying by the tun or half-tun (pipe) was the economical choice for large households.

[Postscript: A disappointing picture for this post, I know. As I mentioned in my last post, I lack enough pictures on medieval economic history and products, so I’m switching to some new topics in future posts to give some better or relevant photos some airtime.]