The main similarity of the two methods is that they both involve curves. A chart or table also shows the options that are available at a certain level of input. Drawing a curve suggests there are intermediate production or consumption options, even if they are not specifically listed on a table, which are available at locations along the curve. According to Middlebury College, an isoquant map includes all possible production choices. An indifference map includes all available consumption choices.
Both curves assume that the user is attempting to maximize returns. The edge of the isoquant is the maximum that the company can produce, and the edge of the indifference curve is the maximum amount the consumer can purchase. Failing to maximize returns provides a return that is below the line of the curve. According to Seattle University, both graphs assume the curve represents the most efficient use of resources available.
Marginal returns are a feature of both types of graphs. The isoquant curve shows the result of adding a resource to production, such as additional workers. At first, adding more workers makes the firm able to produce more products at an increasing rate, but eventually adding another additional worker will not increase production by the same amount. This is similar to the marginal return in an indifference curve. A thirsty person receives great benefit when receiving one bottle of water, receiving the thousandth bottle of water isn't as impressive.
Tradeoffs are a feature of both isoquants and indifference curves. Producing more of one item at the factory reduces the amount of the other item the factory produces, and the chart shows two items. The isoquant does not show the potential byproducts that customers might also purchase, or allow for the possibility that the production inputs are not fully interchangeable. For an indifference curve, the consumer only chooses between two items, such as chicken or beef. The model does not mention that the consumer may be able to purchase fish instead.