Nursing Math Cheat Sheet — All Formulas & Reference Tables

The Core Nursing Math Formulas

A nursing math cheat sheet collects the formulas nurses use most: drug dose = Desired ÷ Have × Quantity; IV flow rate = Volume ÷ Time (hrs); IV drip rate = (Volume × drop factor) ÷ time in minutes; and the core conversion, 1 mg = 1,000 mcg. The full formula set, normal lab values and unit conversions are listed below.

💊 Drug Calculation Formulas

Liquid Drug Dose

Volume = (Desired ÷ Have) × Quantity

Tablets / Capsules

Tablets = (Desired ÷ Have) × 1 tablet

Pediatric (mg/kg)

Dose = Weight (kg) × mg/kg ordered

BSA Dose

Dose = BSA (m²) × dose/m²

💧 IV Calculation Formulas

IV Flow Rate (mL/hr)

Rate = Volume (mL) ÷ Time (hrs)

IV Drip Rate (gtt/min)

gtt/min = (Vol × Drop factor) ÷ (Time hrs × 60)

Infusion Duration

Hours = Volume (mL) ÷ Rate (mL/hr)

mcg/kg/min → mL/hr

mL/hr = (mcg/kg/min × kg × 60) ÷ mcg/mL conc.

🧮 Body Measurement Formulas

BMI

BMI = Weight (kg) ÷ Height² (m)

BSA (Mosteller)

BSA = √(Height cm × Weight kg ÷ 3600)

IBW Male (Devine)

IBW = 50 + 2.3 × (Height in − 60)

IBW Female (Devine)

IBW = 45.5 + 2.3 × (Height in − 60)

Adjusted Body Weight

ABW = IBW + 0.4 × (Actual − IBW)

Mean Arterial Pressure

MAP = (Systolic + 2 × Diastolic) ÷ 3

🫘 Renal Formulas

CrCl (Cockcroft-Gault)

CrCl = [(140−age) × wt × 0.85*] ÷ (72 × SCr)
*females only

eGFR (MDRD)

175 × SCr⁻¹·¹⁵⁴ × Age⁻⁰·²⁰³ × 0.742* × 1.212**
*female **Black

Parkland Formula

Total 24hr = 4 × Weight (kg) × %TBSA
½ in first 8hrs, ½ in next 16hrs

Fluid Balance

Balance = Total Intake − Total Output

🔬 Normal Lab Values

Lab Test	Normal Range	Units
pH (arterial)	7.35 – 7.45	—
PaCO₂	35 – 45	mmHg
PaO₂	80 – 100	mmHg
HCO₃⁻	22 – 26	mEq/L
Sodium (Na⁺)	135 – 145	mEq/L
Potassium (K⁺)	3.5 – 5.0	mEq/L
Chloride (Cl⁻)	98 – 106	mEq/L
Bicarbonate (HCO₃⁻)	22 – 29	mEq/L
Glucose (fasting)	70 – 99	mg/dL
BUN	7 – 20	mg/dL
Creatinine (male)	0.7 – 1.3	mg/dL
Creatinine (female)	0.5 – 1.1	mg/dL
Haemoglobin (male)	13.5 – 17.5	g/dL
Haemoglobin (female)	12.0 – 15.5	g/dL
WBC	4,500 – 11,000	/μL
Platelets	150,000 – 400,000	/μL
INR (therapeutic)	2.0 – 3.0	—

🔄 Unit Conversions

Weight

1 kg = 2.20462 lb
1 lb = 0.45359 kg
1 stone = 6.35029 kg

Length

1 inch = 2.54 cm
1 foot = 30.48 cm
1 m = 100 cm = 39.37 in

Drug Mass

1 g = 1,000 mg
1 mg = 1,000 mcg
1 mcg = 1,000 ng

Temperature

°F = (°C × 9/5) + 32
°C = (°F − 32) × 5/9
K = °C + 273.15

Volume

1 L = 1,000 mL
1 mL = 1 cc
1 tablespoon = 15 mL
1 teaspoon = 5 mL

Blood Sugar

mmol/L = mg/dL ÷ 18.016
mg/dL = mmol/L × 18.016

📋 Quick Clinical Reference

Normal Vital Signs (Adult)

BP: 90–120 / 60–80 mmHg
HR: 60–100 bpm
RR: 12–20 breaths/min
Temp: 36.1–37.2°C (97–99°F)
SpO₂: ≥ 95%

Urine Output Targets

Adult: 0.5–1.0 mL/kg/hr
(≈ 30–50 mL/hr for 70 kg adult)
Child: 1.0 mL/kg/hr
Infant: 2.0 mL/kg/hr

MAP Targets

Normal: 70–100 mmHg
Minimum perfusion: ≥ 60 mmHg
Sepsis target: ≥ 65 mmHg

GCS (Glasgow Coma Scale)

Eyes: 1–4 · Verbal: 1–5 · Motor: 1–6
Max: 15 (normal)
Intubation indicated: ≤ 8
Severe TBI: ≤ 8

Printable Cheat Sheets

Focused one-page sheets, each formatted to print cleanly for a clipboard or folder.

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Reference Guides

Frequently Asked Questions

What is the basic nursing dosage formula?

Desired ÷ Have × Quantity (D/H × Q). For an order of 500 mg where stock is 250 mg in 5 mL: 500 ÷ 250 × 5 = 10 mL. Both values must be in the same unit before you divide.

How do you calculate IV drip rate in gtt/min?

Volume (mL) ÷ time (minutes) × drop factor (gtt/mL). For 1,000 mL over 8 hours (480 minutes) with a 15 gtt/mL set: 1,000 ÷ 480 × 15 = 31 gtt/min.

What is the formula for mcg/kg/min to mL/hr?

(Dose mcg/kg/min × weight kg × 60) ÷ concentration in mcg/mL. Convert the bag strength from mg to mcg first — that unit step is where most errors creep in.

How many mcg are in 1 mg?

1,000 micrograms in 1 milligram, and 1,000 milligrams in 1 gram. To convert mg to mcg multiply by 1,000; to go the other way, divide by 1,000.

This cheat sheet is for educational reference only. Always use current institutional drug references and consult with pharmacists or physicians for clinical decisions.