A cross-country assessment of the cost of carbon sequestration in the forest sector is needed for planning and achieving climate commitments, such as the Paris Agreement, at global, regional, national, or sectoral scales. We provide a global and bottom-up assessment of the break-even carbon price to undertake forest plantation and forest conservation at a country level for 166 nations. We construct a global dataset of key cost factors, examine their global distributions, and undertake a cross-country assessment of cost differences with alternative forest programs (plantation and conservation). Our bottom-up approach is also calibrated to sub-national case studies to investigate the average cost of forest carbon in Australian states and Canadian provinces. We find that the break-even carbon price varies by countries, locations within a country, forest programs and co-benefits. Our estimates provide an approximation of the cost-effectiveness of forest carbon sequestration relative to non-forest climate mitigation approaches.