Gumaca is located along the eastern coast of the Province of Quezon. The town of Plaridel in the Northwest; Lamon Bay on the northeast; Macalelon on the southeast; Pitogo and Unisan on the southwest bound it. Gumaca is situated on the bank of the Pipisik River and Lamon Bay, which are both navigable throught the use of bancas and motor boats. It is 196 kilometers southeast of Lucena City. It is strategically situated at the crossroads of the Maharlika Highway going to Bicol and Bondoc Peninsula.
Gumaca has an area of 22,220 hectares composed of fifty nine (59) barangays with the total population of 69,103 for CY 2006. It consists 13,862 households. The barangays are classified into two; rural and urban areas. Nine barangays are considered urban barangays and fifty others are barangays. There are 18 barangays found in Coastal Area.
The slope of the municipality ranges from 0-3, to 3-8 and 8-15. Broad to level to nearly level are classified under 0-3 slope. These are generally the flat plain level lands covering Barangays Adia Bitaog, Bantad, Biga, Binambang, Camohaguin, Casasahan Ibaba, Casasahan Ilaya, Cawayan, Gitnang Barrio, Hagakhakin, Mabunga, Mataas na Bundok, Panikihan, Progreso, Rosario, San Juan de Jesus, San Vicente, Sastre, Tumayan, Villa Arcaya and Villa Bota. Remaining barangay have a 3-8% slope, and barangay Tumayan have slopes of 8-15%. These are gently undulating and rolling lands sloping in more than one general direction.