Medical Calculation Formula

by | May 26, 2025 | Nurse Article, Nursing Important Questions, Nursing Notes | 0 comments

We have given complete list of medical calculation formula.

Medical Calculations

1. BMI

BMI = Weight (kg) / Height (m)²

2. BSA – Mosteller formula

BSA = √[(Height(cm) × Weight(kg)) / 3600]

3. IV Drip Rate

gtt/min = (Volume × Drop Factor) / Time (min)

4. Infusion Rate

mL/hr = Total Volume / Time (hr)

5. Dosage Calculations

Dose = mg/kg × Weight(kg)

6. Pediatric Fluid Requirements (4:2:1 Rule)

4 mL/kg/hr (first 10 kg), 2 mL/kg/hr (next 10 kg), 1 mL/kg/hr (>20 kg)

7. % Drug Solution

1% = 1g/100mL = 10 mg/mL

8. Creatinine Clearance

CrCl = [(140 – age) × weight (kg)] / (72 × serum creatinine) × 0.85 (if female)

9. eGFR

MDRD or CKD-EPI formulas (based on lab)

10. Anion Gap

AG = Na⁺ – (Cl⁻ + HCO₃⁻)

11. Corrected Sodium (Hyperglycemia)

Corrected Na = Measured Na + [1.6 × ((Glucose – 100)/100)]

12. Corrected Calcium

Corrected Ca = Measured Ca + 0.8 × (4 – albumin)

13. Alveolar Gas Equation

PAO₂ = FiO₂ × (Patm – PH₂O) – PaCO₂ / RQ

14. A-a Gradient

A–a gradient = PAO₂ – PaO₂

15. P/F Ratio

P/F Ratio = PaO₂ / FiO₂

16. MAP

MAP = (SBP + 2 × DBP) / 3

17. Pulse Pressure

PP = SBP – DBP

18. Cardiac Output / Index

CO = HR × SV | CI = CO / BSA

19. Heart Rate (ECG)

HR = 300 / Number of large squares between R-R

20. APGAR Score

Appearance, Pulse, Grimace, Activity, Respiration (0–10)

21. Weight-Based Drug Dosing

Dose = mg/kg × Weight

22. Estimated Weight by Age

1–10 yrs: (Age × 2) + 8

23. BP Percentiles

Use age, sex, and height to assess percentile

24. Naegele’s Rule

EDD = LMP + 1 year – 3 months + 7 days

25. Bishop Score

Assesses cervical readiness for labor (0–13)

26. Contraction Frequency

Count contractions in a 10-minute window

27. GCS

Eye (4) + Verbal (5) + Motor (6) = 3–15

28. Shock Index

SI = HR / SBP

29. Wells Score

DVT/PE clinical prediction (score-based)

30. CHA₂DS₂-VASc Score

Stroke risk in AF (0–9)

31. Insulin Dose

Based on sliding scale or carb ratio

32. HbA1c to eAG

eAG = (28.7 × HbA1c) – 46.7

33. Insulin-Carb Ratio

ICR = 500 / TDD

34. Sodium Correction

Use formulas for hypo/hypernatremia adjustment

35. Potassium Replacement

10 mEq K⁺ ≈ 0.1 mEq/L serum increase

36. Osmolality

Osm = 2 × Na + Glucose/18 + BUN/2.8