Usually they are 5 - 10 times stronger than the herb itself. I often tell newcomers that extracts are like very concentrated teas. Most extracts are made with the liquid solvents of distilled water, grain alcohol and vegetable glycerin. The herb material is soaked or infused in the solvents for a period of time before the herb is strained out and the liquid has taken on the properties of the herb. Both extracts and tinctures are made in this way.
Tinctures generally have a higher alcohol content.
That is why you will usually find a higher dose with a tincture. Doses are usually achieved by counting drops or taking a dropperful. Drops can be taken directly into the mouth or under the tongue and liquid consumed afterwards or drops can be put into a cup of water. If you are sensitive to alcohol, consider what Jeff does. He mixes drops of the extract into a cup of water just off the boil, lets it sit for 5 minutes and he experiences no problems.