Meq and mmol Calculation
Information
For a webbased calculator for electrolytes, click here.
Basic
meq and mmol calculations:
· mmol = molecular weight (MW) in mg
· 1meq = 1mmol ¸ # of charges
· Charges is defined as the total number of positive OR negative charges, but NOT
positive and negative charges added together.
· Example:
– Ca^{++} gluconate^{ } (MW = 430)
– 1 mmol of calcium gluconate = 430mg
– Ca gluconate has two positive and two negative charges
– 1meq Ca gluconate = 430mg ¸ 2 = 215mg
– When converting mg to meq, the number of meq to mmol is the number of charges.
For example, in the case of Ca gluconate, there are 2 meq for every mmol
because there are 2 charges. (1mmol = 430mg; 430mg/215mg = 2meq;
1mmol = 2meq of Ca gluconate)
More
about the molecular weight:
· The molecular weight may be more than just the salt you’re using. For
example, magnesium sulfate (Mg^{++}SO_{4}^{ }; MW = 120.36) is available
commercially as magnesium sulfate heptahydrate (Mg^{++}SO_{4}^{ }·7H_{2}0;
MW = 246.47). In this case, you would use the molecular weight of
magnesium sulfate heptahydrate since that is what you actually have.
Mmol and meq of
Phosphates:
· NaPO_{4} and KPO_{4 }exhist as a mixture of monobasic and dibasic (monobasic KPO_{4 }
and dibasic K_{2}PO_{4 }
· 3mmol of NaPO_{4 }= 4meq of NaPO_{4}
· 3mmol of KPO_{4 }= 4.4meq of KPO_{4}
· mmol is used to express the phosphate and meq used to express Na or K
· Because of dibasic form, there will be more Na or K than PO_{4}. Therefore, meq will
always be the larger number.
· 3mmol of KPO_{4 } mixture contains 93mg of phosphorus (MW = 31) (NOT
PHOSPHATE although I’m not sure why) and 170.3mg of K (MW = 39.1)
170.3mg 
1mmol 
1meq 
= 
4.4meq of
K 

39.1mg 
1mmol 
93mg 
1mmol 
= 
3mmol of
PO_{4} 

31mg 
· 3mmol of NaPO_{4 } mixture contains 93mg of phosphorus (MW = 31) (NOT
PHOSPHATE although I’m not sure why) and 92mg of Na (MW = 23)
92mg 
1mmol 
1meq 
= 
4meq of
Na 

23mg 
1mmol 
93mg 
1mmol 
= 
3mmol of
PO_{4} 

31mg 