Sustainability has long been a topic of substantial interest to the design and human-centered computing communities. With industries increasingly prioritizing climate targets, there is a growing demand for sustainable product design. This article addresses this need through EcoSketch, a digital tool designed to democratize environmental impact assessments for product designers. Shifting typically retrospective evaluations to the early stages of product development, EcoSketch enables proactive consideration and adoption of sustainable alternatives. Unlike software tailored to environmental scientists, it minimizes the need for specialized training or extensive data inputs. We delve into the development and evaluation of EcoSketch, highlighting its unique features and usability strengths. This article concludes by discussing design implications and proposing future research avenues to strengthen the intersection of human-computer interaction and sustainable product design, with the aim of advancing progress on environmental challenges at the systems level.