Background: Calcium is an essential nutrient for bone and overall health, yet women in low-resource settings are disproportionately at risk of deficiency. Bihar, a state of India, is characterized as a region where sociocultural and economic barriers aggravate nutritional disparities. Objectives: The objective of the study was to investigate the prevalence of insufficient calcium intake and supplement use among women aged 35–65 years in Sitamarhi district, Bihar, and also examine the influence of socioeconomic factors on dietary practices. Methods: A community-based cross-sectional study was conducted involving 500 women selected by stratified random sampling from five blocks of Sitamarhi. Data were collected through standardized questionnaires and observation-based checklists. Descriptive statistics summarized sociodemographic characteristics, while chi-square tests evaluated associations between income, education, occupation, family type, and adequacy of calcium intake. Results: The study indicated that 41% of respondents came from families earning less than INR 10,000 per month, whereas 30% were illiterate. Homemakers represented 56% of the sample, indicating financial dependency on male family members. Only 13% of individuals consumed milk daily, but more than 70% rarely or never consumed dairy products, with affordability (65%) and disliking (17%) as major barriers. Only 28.7% of participants reported adequate calcium intake, while 71.3% exhibited deficiencies. Supplement use was low (23.3%). Age, education, occupation, income, and family type were significantly associated with calcium intake (p < 0.05). Younger women (35–45 years), those with higher education, stable income, and employment were more likely to meet calcium requirements.  Conclusions: The study suggests that poverty, illiteracy, cultural norms, and inadequate health education contribute substantially to low calcium intake among rural women. Policy measures such as subsidized dairy schemes, fortified food distribution through public systems, community-based nutrition education, and gender-sensitive interventions are recommended to bridge socioeconomic gaps and improve women’s bone health.