Assize of Bread Calculator
Simulate the medieval English law that scaled bread weight inversely with grain prices.
Last reviewed: June 2026Price Scenario Table
| Wheat Price (d/qtr) | Loaf Weight (oz) | Weight (g) | Change |
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What this calculator reconstructs
The Assize of Bread was a medieval English bread regulation that linked the weight of a fixed-price loaf to the market price of wheat. Instead of asking shoppers to pay a different coin price every time grain became dearer or cheaper, the assize changed the loaf weight. A farthing loaf, halfpenny loaf, or penny loaf kept its money price, but the amount of bread changed as the quarter price of wheat changed.
This calculator turns that idea into a simple interactive model. Enter a baseline wheat price, a current wheat price, and a baseline farthing-loaf weight. The result shows the legal loaf weight implied by the same inverse relationship, the gram conversion, the percent change, and a scenario table for other wheat prices.
Formula used
The calculation is intentionally simple: current loaf weight = baseline loaf weight x baseline wheat price / current wheat price. If the current wheat price is twice the baseline price, the loaf is half as heavy. If the current wheat price is half the baseline price, the loaf is twice as heavy. That is the economic relationship the page is designed to demonstrate.
The original assize sources include detailed tables for different bread classes and period-specific weight notation. This calculator is not trying to reproduce every row of those tables. It is a teaching model for the core mechanism: fixed coin price, variable loaf weight, and a baker's margin built into the regulated schedule.
How to choose inputs
Base Wheat Price is the reference price for a quarter of wheat. Current Wheat Price is the price you want to compare against that reference. The unit label uses pence per quarter because that is a natural way to model medieval grain prices, but you can use any consistent unit as long as both price fields use the same unit.
Base Loaf Weight is the reference weight for the loaf at the baseline price. The calculator labels it as a farthing loaf because that was a common way to discuss fixed-price bread, but the same inverse relationship can be used for another loaf denomination if you enter the appropriate baseline weight.
Worked examples
Default example: the default values use a 3d baseline wheat price, a 6d current wheat price, and a 68 oz baseline loaf. Because the current price is twice the baseline, the result is 34.00 oz, about 963.88 g, and a -50.0% weight change.
Price returns to baseline: if base price and current price are both 3d, the loaf remains 68.00 oz. The weight change is 0.0% because grain is being priced at the same reference point.
Dear grain scenario: if the current price rises to 12d while the baseline remains 3d, the current price is four times the baseline. The loaf falls to 17.00 oz, which is one quarter of the baseline weight.
What the Assize of Bread regulated
The medieval rule was about market supervision, not recipe design. It regulated the price, weight, and quality of bread and ale sold in towns and villages. Historical texts describe named bread types such as wastel, cocket, simnel, whole-wheat, and household-style bread, with different weights because flour quality and bread class mattered.
The practical idea was consumer protection in a market where bread was a staple food and grain prices could move sharply. Buyers could expect a fixed coin price for a recognizable loaf class, while local officials could adjust the required weight when wheat prices changed. Bakers were also allowed specified gains and expenses, which is why the assize is best understood as a regulated market schedule rather than a pure nutrition or recipe formula.
Reading the scenario table
The scenario table keeps your baseline price and baseline loaf weight fixed, then calculates what the loaf would weigh at common wheat prices. It is useful for classroom demonstrations, historical-economics notes, and comparing how sensitive regulated bread weight was to grain-price shocks.
For example, with a 3d baseline and 68 oz loaf, the table shows 34.0 oz at 6d and 17.0 oz at 12d. Those rows make the inverse relationship visible: every doubling of wheat price halves the regulated loaf weight.
Limitations and unit caveats
Historical assize tables used medieval currency, grain measures, and weight notation. A quarter of wheat was not a modern consumer package, and medieval pounds, shillings, pence, and ounce references do not always map neatly onto modern avoirdupois units. The calculator uses decimal pence and modern ounces so visitors can explore the relationship without first learning every historical unit convention.
Use the result as an educational reconstruction. It should not be used to price modern bread, estimate baking ingredients, set legal weights, evaluate nutrition, or infer a household food budget. For modern baking math, use a recipe scaler or baker's percentage tool instead.
Sources
This page is aligned with the Fordham Medieval Sourcebook text of the Assizes of Bread, Beer, and Lucrum Pistoris and Alan S. C. Ross's Economic History Review article on the Assize of Bread.