In rice crop, herbicide applications are often made using conventional manual spraying equipment. In India, recent advancements in aerial spraying technology, which includes unmanned aerial vehicles, have great potential to replace conventional knapsack sprayers. In our study, an unmanned aerial vehicle (UAV) (15 L/ha, 20 L/ha and 25 L/ha) and knapsack sprayer (KS)(500L/ha) with pre-emergence (PE) application of pyrazosulfuron ethyl (10%WP) at 25 g a.i./ha at 3 days after transplanting (DAT) and post-emergence (PoE) application of bis-pyribac Sodium (10%SC) at 25 g a.i./ha at 25 DAT were used to compare the droplet deposition characteristics for different spray volumes in rice field. The results revealed that the KS (500 L/ha) had a higher droplet coverage rate, droplet size (Dv0.5), number of spray deposits/cm2 and spray uniformity in comparison with UAV spray volumes. Among UAV spray volumes, the application of 25 L/ha had better coverage rate, spray uniformity and the number of spray deposits/cm2. UAV (25 L/ha) recorded optimum droplet characteristics for herbicide application. Considering the low volume application of UAV (25 L/ha) as compared with high volume KS (500 L/ha), it is better to go for the optimal application of UAV (25 L/ha), which is energy efficient and cost-effective, labour-saving approach compared to conventional knapsack sprayer.