Cask Directory Guide
RLA & ROA Explained: Measuring Alcohol in a Cask
In the rum and whisky cask industry, RLA (Regauged Litres of Alcohol) and ROA (Regauged Original Alcohol) refer to different ways of measuring the alcohol content in a cask.
RLA – Regauged Litres of Alcohol
Definition: The current amount of pure alcohol in the cask, measured after regauging (i.e., re-measuring) its strength and volume.
Calculation:
- Bulk Litres = total volume of liquid in the cask (including water and alcohol)
- ABV = current alcohol by volume percentage
Purpose: Used to determine the actual remaining alcohol content in a cask at any given time, considering evaporation (angel's share).
ROA – Regauged Original Alcohol
Definition: The original amount of pure alcohol in the cask when it was first filled, adjusted for losses over time.
Calculation:
Purpose: Helps track how much alcohol has been lost due to evaporation since the liquid was first casked.
Key Difference between RLA and ROA
- RLA tells you how much alcohol is currently in the cask.
- ROA tells you how much alcohol was originally in the cask at the time of filling.
Both measurements are crucial in the cask trading industry, as they help buyers understand how much liquid is left in a cask and how it has evolved over time.
RLA: Formula to Calculate the Number of Bottles
To calculate the number of bottles you can get from a cask using the RLA (Regauged Litres of Alcohol), you need to factor in the desired bottling strength (ABV) and the bottle size.
- RLA = the current pure alcohol content in the cask.
- Bottling ABV (%) = the alcohol percentage at which the liquid will be bottled (e.g., 40%, 46%, 50%...).
- Bottle Size (Litres) = the volume of each bottle (e.g., 0.7L for a standard bottle, or 0.75L in the US).
Example Calculation
Let's assume:
- RLA = 150 Litres of Alcohol
- Bottling Strength = 46% ABV
- Bottle Size = 0.7 Litres
Key Considerations
- Losses during bottling – Some liquid is lost in the process due to filtration, transfer, etc. You might assume a small percentage loss (e.g., 1-3%).
- Cask Sediments – Some liquid might be left behind due to residue or inefficiencies in draining the cask.
- Cask Strength vs. Dilution – If bottling at cask strength (without dilution), you don't need to adjust for ABV.
ROA: Formula to Calculate the Number of Bottles
To calculate the number of bottles from the ROA (Regauged Original Alcohol), you need to factor in how much of the original alcohol remains in the cask, along with the bottling ABV and bottle size.
Thus, a more accurate formula includes the RLA-to-ROA ratio:
Since:
You can simplify the formula to:
Example Calculation
Let's assume:
- ROA = 200 Litres of Alcohol (original pure alcohol in the cask)
- RLA = 150 Litres of Alcohol (current pure alcohol after angel's share)
- Bottling ABV = 46%
- Bottle Size = 0.7L
- Calculate the Remaining Alcohol Ratio:
- Apply to the formula:
Key Differences Between ROA and RLA for Bottling
- RLA (Regauged Litres of Alcohol) reflects the current state of the cask.
- ROA (Regauged Original Alcohol) represents the starting point, so you must apply a correction factor for evaporation.
If you already have the RLA, it's easier and more accurate to calculate directly from that. ROA is more useful for tracking how much alcohol was lost over time.
Find Casks with Clear RLA and ROA Documentation
Cask.directory connects buyers directly with producers, brokers and independent bottlers offering whisky, rum, cognac, armagnac, calvados and other mature spirits casks.
Find a Cask