Alcohol Dilution Calculators

Intended Use of the Calculators

The calculators are for use in diluting ethyl alcohol (ethanol) or isopropyl alcohol (isopropanol) with water. The accuracy of the results from the calculator is sufficient for home and some commercial use.

Some Examples of Use:

• You have a liter of 95% (by volume) ethyl alcohol and you want to know how much (distilled) water you need (in weight or volume) to add in order to end up with 70% ethyl alcohol and how much (in weight and volume) alcohol you end up with.
• Given 1,000 grams of 70%v/v alcohol, you'd like to know how much water (in weight or volume) is needed to dilute it down to 60%.
• You want to know how much (whether in weight or volume) 99% isopropyl alcohol and water you need to make 36 fluid ounces (or some other unit of volume) of 50% alcohol.
• You wish to find out the resulting concentration of the alcohol when you mix a gallon of 80% ethyl alcohol and half a gallon of water, or perhaps 2.5 liters of alcohol and 400 grams of water.

Assumptions

• Concentrated alcohol is assumed to be composed solely of alcohol and water
• Water and alcohol are the only ingredients considered. Any impurity is not taken into account
• Water is considered to have zero cost
• Alcohol and water are at the same temperature
• Diluted alcohol v/v concentration must be greater than 35%v/v

Technical Notes

• Alcohol v/v concentrations are temperature dependent. Thus the calculators will require the user to enter a "reference temperature" at which the v/v concentration is specified at. This will usually be 20 or 25°C.
• Volume loss that occurs when alcohol and water are mixed is taken into account by the calculators. Percentage of volume loss is provided. Formula used is: \( 1 - \frac {actual\ volume\ of\ diluted\ alcohol} {volume\ of\ concentrated\ alcohol\ + volume\ of\ added\ water} \)
• Values for concentration weight/weight and corresponding density are taken from alcoholometric tables for isopropanol and ethanol. Regression analysis was used to derive equations to compute for various values
• Data for regression equations were limited to the range of 36% to 100%v/v concentration (30% to 100%w/w) because 40% was deemed to be the lower bound for ordinary (non-food) applications of ethanol and isopropanol
• All weights entered by user are converted to kilograms and all volumetric values are converted to liters because all constants and equations used internally are in metric units
• Conversion factors for weight and volume are from Appendix B of Guide for the Use of the International System of Units (SI)
• "Weight" is used throughout this page rather the technically more correct term "mass."

Spreadsheet Version

• The calculators are also available in downloadable spreadsheet form. Note that the spreadsheet version is in metric units only (grams and milliliters). It also does not have the option for a reference temperature. Alcohol v/v concentrations are assumed to be specified at the same temperature as the alcohol and water.

Equations

• A comprehensive discussion and derivation of the equations used in the calculators as well as tables of concentration and density for isopropanol and ethanol at different temperatures can be found here

Terms Used

Term	Definition
Concentrated alcohol	the alcohol that you have, whose concentration (in %volume/volume) you know, and which you want diluted by adding water
Diluted alcohol	the alcohol that you obtain after adding water to the concentrated alcohol
Initial alcohol concentration	concentration, in %v/v, of the concentrated alcohol
Final alcohol concentration	concentration, in %v/v, of the diluted alcohol
Reference temperature	the temperature at which the alcohol v/v concentration is specified. This will probably be either 20 or 25°C
Current temperature	the actual, present temperature of the concentrated alcohol and water to be added, and therefore the temperature of the diluted alcohol as well

Which Calculator to Use?

There are two calculators to choose from:

Calculator A

INSTRUCTIONS:

1. When typing in numbers, do not enter any spaces or commas. Other than digits, the decimal point (dot) is the only non-numeric character that will be recognized. A number that contains spaces or any other non-numeric character other than a single decimal point (dot) is not considered a valid input and will be ignored.
2. Enter all of the requested values in Table A1
3. In Table A2 enter one and only one of the values and select your preferred units for both weight and volume
4. You may enter requested value for Table A3 if desired
5. Click on the CALCULATE button
6. Results will appear in Table A4
   
   

Table A1 : Required Information

Select or enter values for all of the following items
Type of alcohol	isopropyl (isopropanol) ethyl (ethanol)
Current temperature of alcohol and water (volume of the liquids is temperature-dependent)	15°C (59°F) 20°C (68°F) 25°C (77°F) 30°C (86°F) 35°C (95°F)
Reference temperature of alcohol concentrations (v/v concentration is temperature-dependent)	15°C (59°F) 20°C (68°F) 25°C (77°F) 30°C (86°F) 35°C (95°F)
Initial alcohol concentration at reference temperature (concentration of the alcohol to be diluted)	%vol/vol (minimum value is 36%)
Final alcohol concentration at reference temperature (concentration of the diluted alcohol)	%vol/vol (minimum value is 36%)

Table A2 : More Necessary Information

Enter the value for one and only one of the following four items			Select preferred units for both weight and volume
W E I G H T	Weight of concentrated alcohol (weight of the alcohol to be diluted)		grams kilograms ounces (avoirdupois) pounds (avoirdupois)
	Weight of diluted alcohol (weight of concentrated alcohol + added water)
V O L U M E	Volume of concentrated alcohol (volume of the alcohol to be diluted)		milliliters liters US fluid ounces US gallons imperial fluid ounces imperial gallons
	Volume of diluted alcohol (volume of concentrated alcohol and added water)

Table A3 : Optional Information

	Value	Units
Cost of concentrated alcohol		any currency per unit volume

Table A4a : Summary of Data Provided by the User

Information	Value
Type of alcohol
Current temperature of alcohol and water
Reference temperature of alcohol concentrations
Initial alcohol concentration at reference temperature
Final alcohol concentration at reference temperature
Preferred unit of weight
Preferred unit of volume
Cost of concentrated alcohol

Table A4b : Computation Results

Information		Value	Units
W E I G H T	Weight of concentrated alcohol (weight of alcohol to be diluted)
	Weight of water (weight of water needed to dilute the concentrated alcohol)
	Weight of diluted alcohol (weight of concentrated alcohol + added water)
V O L U M E	Volume of concentrated alcohol (volume of alcohol to be diluted)
	Volume of 100% alcohol (volume of pure alcohol if separated from all the water)
	Volume of added water (volume of water needed to dilute the alcohol)
	Volume of diluted alcohol (volume of concentrated alcohol and added water)
	Volume loss due to contraction		%
C O N C	Initial alcohol concentration at current temperature (concentration of the alcohol to be diluted)		%v/v
	Final alcohol concentration at current temperature (concentration of the diluted alcohol)
C O N C	Initial alcohol concentration (concentration of the alcohol to be diluted)		%w/w
	Final alcohol concentration (concentration of the diluted alcohol)
C O S T	Total cost		any currency of choice
	Cost per unit volume

Calculator B

INSTRUCTIONS:

1. When typing in numbers, do not enter any spaces or commas. Other than digits, the decimal point (dot) is the only non-numeric character that will be recognized. A number that contains spaces or any other non-numeric character other than a single decimal point (dot) is not considered a valid input and will be ignored
2. Enter all of the requested values in Table B1
3. In Table B2 enter the requested pair of values and select your preferred units for both weight and volume
4. You may enter requested value for Table B3 if desired
5. Click on the CALCULATE button
6. Results will appear in Table B4.
   Note that final alcohol concentration will be displayed in red if it is less than 36.0%v/v

Table B1 : Required Information

Select or enter values for all of the following items
Type of alcohol	isopropyl (isopropanol) ethyl (ethanol)
Current temperature of alcohol and water (volume of the liquids is temperature-dependent)	15°C (59°F) 20°C (68°F) 25°C (77°F) 30°C (86°F) 35°C (95°F)
Reference temperature of alcohol concentration (v/v concentration is temperature-dependent)	15°C (59°F) 20°C (68°F) 25°C (77°F) 30°C (86°F) 35°C (95°F)
Initial alcohol concentration at reference temperature (concentration of the alcohol to be diluted)	%vol/vol (minimum value is 36%

Table B2 : More Necessary Information

Enter two values: 1. Desired weight or volume of the alcohol to be diluted, and 2. Desired weight or volume of water to be added			Select preferred units for both weight and volume
W E I G H T	Weight of concentrated alcohol (weight of the alcohol to be diluted)		grams kilograms ounces (avoirdupois) pounds (avoirdupois)
	Weight of water to be added
V O L U M E	Volume of concentrated alcohol (volume of the alcohol to be diluted)		milliliters liters US fluid ounces US gallons imperial fluid ounces imperial gallons
	Volume of water to be added

Table B3 : Optional Information

	Value	Units
Cost of concentrated alcohol		any currency per unit volume

Table B4a : Summary of Data Provided by the User

Information	Value
Type of alcohol
Current temperature of alcohol and water
Reference temperature of alcohol concentration
Initial alcohol concentration at reference temperature
Preferred unit of weight
Preferred unit of volume
Cost of concentrated alcohol

Table B4b : Computation Results

Information		Value	Units
W E I G H T	Weight of concentrated alcohol (weight of alcohol to be diluted)
	Weight of water (weight of water needed to dilute the concentrated alcohol)
	Weight of diluted alcohol (weight of concentrated alcohol + added water)
V O L U M E	Volume of concentrated alcohol (volume of alcohol to be diluted)
	Volume of 100% alcohol (volume of pure alcohol if separated from all the water)
	Volume of added water (volume of water needed to dilute the alcohol)
	Volume of diluted alcohol (volume of concentrated alcohol and added water)
	Volume loss due to contraction		%
C O N C	Initial alcohol concentration at current temperature (concentration of the alcohol to be diluted)		%v/v
	Final alcohol concentration at current temperature (concentration of the diluted alcohol)
	Final alcohol concentration at reference temperature (concentration of the diluted alcohol)
C O N C	Initial alcohol concentration (concentration of the alcohol to be diluted)		%w/w
	Final alcohol concentration (concentration of the diluted alcohol)
C O S T	Total cost		any currency of choice
	Cost per unit volume