AIM: Radiotherapy is a cornerstone of cancer treatment in India, yet its expansion is hindered by high investment costs. Effective planning and target estimation based on cancer burden are crucial to meet the radiotherapy demands of patients with cancer. METHODS: Data from Australian Collaboration for Cancer Outcomes Research and Evaluation (CCORE) were used. Epidemiological data on stage, subsite and histology from National cancer registry programme were used to assess the optimal utilization proportion for India. A sensitivity analysis was carried out. Similarly optimal radiotherapy fraction has also being calculated. These measures have been used to estimate the existing radiotherapy utilization gap by comparing with the current radiotherapy utilization from cancer registry as well as estimate the optimal radiotherapy machines required for the country. RESULTS: Optimal radiotherapy utilization rate in India is 58.4% (95% CI: 57.6-58.9), whereas the actual utilization rate is 28.5% (95% CI: 28.0-31.5). The estimated number of radiotherapy machines required to meet demand ranges from 1,585 to 2,545. CONCLUSION: The study highlights a substantial shortfall in radiotherapy utilisation across all cancer types and underscores the need for interventions to meet the gap in machines required for an equitable cancer care. Efforts to reduce the cancer burden in the country shall influence the radiotherapy requirement through early stage diagnosis and treatment. Advancement in other modalities of treatment shall need to watch closely.