Pre-K is widely acknowledged to be a sound public investment. When their pre-K programs are of high quality, disadvantaged children see particularly large benefits--higher test scores, less need for grade repetition and special education, and increased educational attainment. Yet high-quality programs are in short supply. State boards of education can change this situation, but they must first figure out how to pay for it. One obvious approach is to incorporate pre-K into the existing K-12 school funding formula. While just 11 states have tried it, inclusion of state-funded pre-K in the school funding formula may well be the best option for extending access to more children. This article evaluates how states that use the K-12 formula to finance pre-K compare with those that do not to show how they all fare with respect to adequacy and equity. Programs in states that are already using the K-12 funding formula for pre-K clearly have benefitted, including weathering the Great Recession much better than pre-K programs in other states. This article discusses an approach that can guide the adaptation of K-12 funding formulas to provide adequate and fair funding for pre-K based on careful appraisals of what is required to achieve a state's goals for its young children.