How many calories are in one seltzer? Your Guide to Calorie-Free Hydration
                                
                                
                                •
                                
                                
                        
                                    
                                    4 min read                                
                            
                                Plain seltzer water, which is simply carbonated water, contains zero calories. However, this can change dramatically with the addition of flavors or alcohol, turning a zero-calorie drink into one that requires careful label-reading to avoid unwanted sugars and additives.