Comparison between a soap and a detergent is given in table below
| SOAPS | DETERGENTS |
| Soaps are sodium salts of higher fatty acids. | Synthetic detergents are sodium alkyl sulphates or sodium alkyl benzene sulphonates with alkyl group having more than ten carbon atoms. |
| Soaps are prepared from natural oils and fats. | Synthetic detergents are prepared from the hydrocarbons of petroleum. |
| Soaps form insoluble salts (curdy white ppt.) with calcium and magnesium which are present in hard water and hence, cannot be used in hard water. | Calcium and magnesium salts of detergents are soluble in water and, therefore, no curdy white precipitates are obtained in hard water and hence, can be used even in hard water. |
| Soaps cannot be used in acidic medium as they are decomposed into carboxylic acids in acidic medium. | They can be used in acidic medium as they are the salt of strong acids and are not decomposed in acidic medium |
| Soaps are biodegradable. | Some of the synthetic detergents are not biodegradable. |
| Soaps are the sodium salts of carboxylic acids in long chains. | Sodium salts of long-chain benzene sulphonic acids are detergents. |