We used C-13 and H-1 NMR spectroscopy to examine the equilibrium speciation in formaldehyde methanol water solutions at moderate formaldehyde concentrations such as those used in the synthesis of formaldehyde-based organic gels. Concentrations of small methylene glycol oligomers and their methoxylated forms found in these solutions were quantitatively determined over a range of formaldehyde concentrations and methanol water ratios, and at temperatures between 10 and 55 degrees C. Using the measured concentrations, equilibrium constants for methylene glycol dimer and trimer formation as well as methoxylation of these oligomers were calculated. Based on this, we developed a quantitative equilibrium model for calculation of formaldehyde-related species concentrations over a range compositions relevant for formaldehyde based sol gel processes allowing for more rational design of formaldehyde polymerization systems.