Global discussions on universal health coverage (UHC) have focussed attention on the need for increased government funding for health care in many low- and middle-income countries. The objective of this paper is to explore potential targets for government spending on health to progress towards UHC. An explicit target for government expenditure on health care relative to gross domestic product (GDP) is a potentially powerful tool for holding governments to account in progressing to UHC, particularly in the context of UHC's inclusion in the Sustainable Development Goals. It is likely to be more influential than the Abuja target, which requires decreases in budget allocations to other sectors and is opposed by finance ministries for undermining their autonomy in making sectoral budget allocation decisions. International Monetary Fund and World Health Organisation data sets were used to analyse the relationship between government health expenditure and proxy indicators for the UHC goals of financial protection and access to quality health care, and triangulated with available country case studies estimating the resource requirements for a universal health system. Our analyses point towards a target of government spending on health of at least 5% of GDP for progressing towards UHC. This can be supplemented by a per capita target of $86 to promote universal access to primary care services in low-income countries.