Learning Blast: Balance Criteria and Constraints

Engineers identify criteria and constraints, using trade-offs to balance competing factors.

When facing complex problems, engineers must balance many technical, economic, environmental, social, cultural, and ethical factors. This usually happens early in the engineering design process. However, it is common for additional criteria and constraints to be identified as questions arise later in the process as potential solutions are developed and tested.  

In engineering, criteria are the requirements of a design. Constraints are limits that restrict the design. Like engineers, youth’s solutions should be guided by criteria and constraints. Criteria and constraints are often in tension and youth may need to consider trade-offs to optimize their solution. Discussing and posting the criteria and constraints can enhance youth’s designs. Throughout the design process, these criteria and constraints should be referenced as the metric for success. 

As you watch the video, think about this:

  • What are the criteria and constraints for this activity? 
  • What strategies or questions do facilitators use to help youth think about the criteria and constraints?  

Watch the video:

Share what you noticed:

  • What did you notice in the video?  
  • How could you engage youth in helping to define the criteria and constraints for an engineering challenge? 
  • How can youth apply this practice in other areas of their life?  Where else do they have to manage trade-offs? 

What we know:

Criteria are the requirements of a design. They may be related to the design or use of the project. For example, criteria for a baby gate that keeps young children from going up a staircase might include  

  • The gate must be adjustable to openings of various widths. 
  • It is at least 22 inches tall and can support a child’s weight up to 30 pounds. 
  • It cannot be opened by children under the age of 5. 
  • Adults can see what is on the other side of the gate and open it without using their hands. 
  • The product uses bright colors and designs. 

Constraints are limits that restrict the design. For the baby gate example, constraints might include the following:  

  • The retail price for the gate needs to be under a given amount. 
  • The design needs to be completed in 6 months. 
  • The gate cannot weigh more than 15 pounds. 
  • The design must meet all U.S. and European safety requirements for young children. 

Criteria and constraints are often in tension. A sturdier gate may weigh more. The cheapest or easiest way to open the gate may not be hands-free. Adhering to safety requirements may limit material choices. As they generate ideas, engineers need to be aware of the many parameters and balance the tradeoffs to optimize a solution that fits as many of the criteria and constraints as possible. 

What you know:

Youth learn about balancing criteria and constraints as they work through the Engineering Design Process. You can support developing this practice by engaging youth in talking about trade-offs between competing factors and encouraging them to make their own decisions. 

You can also help them think about how they must make trade-offs in other areas of life and the consequences of these decisions – if you finish your homework before you start watching videos afterschool, your parents are less likely to get upset with you. This is a practice that develops as you talk with young people about the decisions they are making.

Key Take-Away

Criteria and constraints provide the metrics for successful designs. They are often in tension. As youth develop this engineering practice, they will come to understand that any given solution cannot optimize all the criteria and constraints, and that their role as an engineer is to find the best solution possible within the full context of the problem. 


  • What strategies would you use to get youth more engaged in defining the criteria and constraints for an engineering challenge?  
  • How can using real-world problems make it easier for youth to think about balancing competing factors in their problem-solving? 


Developed in collaboration with Christine M. Cunningham. These practices are also more fully described in educational research articles (Cunningham, 2018; Cunningham & Kelly, 2017).