Back ground: Several studies have established a link between fluid overload and an increased risk of death. After cardiac surgery, patients’ fluid status should be assessed at close intervals. A daily fluid balance (FB) is maintained by the majority of intensive care units (ICUs), which is normally determined using the inputs and outputs recorded charts. Numerous defects exist in such calculations: To begin, they ignore fluid losses due to perspiration, respiration, and diarrhea. This study aims to determine the agreement and correlation between fluid status changes calculated by the daily fluid balance (FB) through the conventional charting approach and Body weight (BW) changes through the use of beds equipped with weighing scales. Additionally, to assess (BW) measurement reliability, we compared (BW) values obtained on ICU discharge using weight-enabled beds to values obtained using a conventional medical scale with high-precision. Patients and method: This is a comparative observational prospective study includes 50 patients after cardiac surgeries. 80% of patients were males and the mean age was 52.9 years. Data were collected from Cardiothoracic Surgery Department data base. It evaluates the precision and usefulness of determining body fluid status and requirements using daily fluid balance and body weight measurements. Results: fifty critically ill adult patients were evaluated; 48 survivors and 2 non survivors. Cumulative 24-h fluid balances rose continuously as well as body weight increase over time. Correction of cumulative fluid balances for insensible perspiration (10 ml/kg/day) also matched with body weight changes. There was highly significant strong positive correlation between overall changes in bodyweight and Cumulative fluid balance p value