Dry Weight & Fluid Balance Calculator

Calculate interdialytic weight gain, UF rate, and fluid overload assessment for dialysis patients.

Medical Disclaimer

This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.

Inputs

Pre-Dialysis Weight (kg)

Target Dry Weight (kg)

Session Duration (hours)

Height (cm)

Age (years)

Sex

Tab to move between fields

Results

Interdialytic Weight Gain

5 kg

≈ 3 bags of sugar

IDWG as % of Dry Weight7.1%

UF Rate1,250 mL/hr

UF Rate per kg17.9 mL/kg/hr

Total Body Water (Watson)40.9 L

Fluid Overload12.2% TBW

How to Use This Calculator

Enter pre-dialysis weight (kg) and the clinically assessed target dry weight (kg).
Enter session duration (hours), patient height (cm), age (years), and sex.
Read interdialytic weight gain (IDWG in kg) — ideally <5% of dry weight.
Review UF rate (mL/hr) and UF rate per kg (mL/kg/hr): keep below 13 mL/kg/hr to reduce hypotension risk.
Use total body water (Watson formula, L) and fluid overload (% TBW) to guide clinical decisions.

How the result changes with Pre-Dialysis Weight (kg)

Pre-Dialysis Weight (kg)	Interdialytic Weight Gain
48	-22 kg
118	48 kg
202	132 kg
272	202 kg

What each input means

Pre-Dialysis Weight (kg): Current weight before the dialysis session.
Target Dry Weight (kg): Clinically assessed euvolemic weight.
Session Duration (hours): Planned hemodialysis session length.
Height (cm): Patient height for TBW calculation.
Age (years): Patient age.
Sex: Biological sex.

What each result means

Interdialytic Weight Gain: Weight gained between dialysis sessions.
IDWG as % of Dry Weight: Should ideally be < 5% of dry weight.
UF Rate: Ultrafiltration rate during the session.
UF Rate per kg: Should be < 13 mL/kg/hr to reduce hypotension risk.
Total Body Water (Watson): Estimated TBW using the Watson formula.
Fluid Overload: Excess fluid as percentage of total body water.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Pre-Dialysis Weight (kg) = 75, Target Dry Weight (kg) = 70, Session Duration (hours) = 4, Height (cm) = 170 = 6 input(s) provided
Calculate Interdialytic Weight Gain
Interdialytic Weight Gain = preWeight - targetDryWeight
5 = 5
Calculate IDWG as % of Dry Weight
IDWG as % of Dry Weight = (idwg / targetDryWeight) * 100
7.1 = 7.1
Calculate UF Rate
UF Rate = (ufVolume * 1000) / (sessionDuration * 60) * 60
1250 = 1250