Dose Calculator

Calculate medication doses based on weight, concentration, and dosing frequency

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Patient Weight

Drug Concentration

Dosing Frequency

Common Medications

Dose Calculator: Complete Medical Dosing Guide

Medication dose calculation is the foundation of safe pharmaceutical practice, determining the exact amount of drug needed based on patient weight, drug concentration, and dosing frequency.Accurate dosing prevents adverse effects, ensures therapeutic efficacy, and is critical for patient safety across all medical specialties from pediatrics to geriatrics.

Our professional dose calculator provides instant, accurate calculations for weight-based dosing with safety checks, volume calculations, and step-by-step verification. Essential for nurses, physicians, pharmacists, and healthcare students working with injectable medications, oral suspensions, and complex dosing regimens.

Quick Answer

To calculate medication doses: Multiply dose per kg by patient weight to get total dose, then divide by drug concentration to get volume. For example: 15 mg/kg × 70 kg = 1050 mg total dose. If concentration is 100 mg/mL, give 10.5 mL per dose. Always verify calculations independently before administration.

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Mathematical Foundation

Dose = (mg/kg) × Weight (kg)

Basic weight-based dosing formula

Essential Formulas:

Weight-Based Dosing

Total Dose (mg) = Dose per kg × Weight (kg)
Volume (mL) = Total Dose (mg) ÷ Concentration (mg/mL)
Daily Dose = Single Dose × Frequency per day

Concentration Conversions

1% solution = 10 mg/mL
1:1000 solution = 1 mg/mL
mg/dL = mg/dL ÷ 100 = mg/mL

Unit Conversions

1 kg = 2.20462 lb
1 mg = 1000 mcg
1 g = 1000 mg
Always use consistent units in calculations

Patient Population Considerations

Pediatric Dosing

Weight-based dosing most accurate for children. Higher per-kg doses often needed.

Neonates (0-28 days): Specialized calculations required
Infants (1-12 months): Use actual weight, monitor closely
Children (1-12 years): Standard mg/kg dosing
Adolescents (12+ years): May use adult doses with weight limits

Special considerations: Immature organ function, different pharmacokinetics

Adult Dosing

Fixed doses common, but weight-based still important for many drugs.

Standard adult: 70 kg (154 lb) reference weight
Obesity: Consider ideal vs. actual body weight
Elderly: May need dose reduction for organ function
Critical care: Often requires weight-based dosing

Applications: Chemotherapy, antibiotics, anticoagulants, anesthetics

Special Populations

Requires modified dosing based on organ function and physiologic changes.

Renal impairment: Dose reduction often needed
Hepatic impairment: Altered drug metabolism
Pregnancy: Consider maternal and fetal safety
Geriatric: Decreased clearance, increased sensitivity

Warning: Always consult specialized references for these populations

Clinical Applications of Dose Calculations

Hospital & Clinical Settings

Injectable Medications

Calculate exact volumes for IV antibiotics, pain medications, and emergency drugs

Pediatric ICU

Critical care dosing for vasopressors, sedatives, and life-support medications

Chemotherapy

Precise dosing based on body surface area and weight for cancer treatment

Emergency Medicine

Rapid calculation of resuscitation drugs, antidotes, and critical medications

Outpatient & Community

Oral Suspensions

Calculate volumes for liquid antibiotics, pain relievers, and pediatric medications

Chronic Disease Management

Weight-based dosing for diabetes, hypertension, and specialty medications

Pharmacy Practice

Verify prescriptions, compound medications, and counsel patients on dosing

Home Healthcare

Calculate doses for visiting nurses and home infusion therapy

Example Problems with Solutions

Example 1: Pediatric Acetaminophen

A 5-year-old child weighs 18 kg. Calculate acetaminophen dose at 15 mg/kg every 6 hours. Suspension concentration is 80 mg/mL.

Single dose = 15 mg/kg × 18 kg = 270 mg

Volume per dose = 270 mg ÷ 80 mg/mL = 3.375 mL

Frequency = every 6 hours = 4 times daily

Total daily dose = 270 mg × 4 = 1,080 mg/day

Maximum daily dose = 90 mg/kg/day = 1,620 mg (within safe limits)

Answer: Give 3.4 mL every 6 hours (270 mg per dose)

Example 2: Adult Antibiotic Dosing

Adult patient weighs 85 kg. Prescribe cefazolin 25 mg/kg IV every 8 hours. Available concentration is 1 g/10 mL.

Single dose = 25 mg/kg × 85 kg = 2,125 mg = 2.125 g

Available concentration = 1 g/10 mL = 100 mg/mL

Volume per dose = 2,125 mg ÷ 100 mg/mL = 21.25 mL

Frequency = every 8 hours = 3 times daily

Total daily dose = 2.125 g × 3 = 6.375 g/day

Answer: Give 21.3 mL IV every 8 hours (2.125 g per dose)

Example 3: Emergency Drug Calculation

Cardiac arrest patient weighs 70 kg. Calculate epinephrine dose at 10 mcg/kg. Available concentration is 1:10,000 (0.1 mg/mL).

Dose = 10 mcg/kg × 70 kg = 700 mcg = 0.7 mg

Available = 1:10,000 = 0.1 mg/mL = 100 mcg/mL

Volume needed = 700 mcg ÷ 100 mcg/mL = 7 mL

Standard epinephrine dose = 1 mg (10 mL of 1:10,000)

Calculated dose is within normal range

Answer: Give 7 mL of 1:10,000 epinephrine IV (0.7 mg)

Medication Safety

High-Alert Medications

Insulin: Units/kg calculation, potential for severe hypoglycemia

Chemotherapy: mg/m² dosing, maximum lifetime doses

Anticoagulants: Bleeding risk, requires monitoring

Vasopressors: mcg/kg/min calculations, titration needed

Calculation Verification

Independent Check: Have another clinician verify calculations

Clinical Judgment: Does the dose make clinical sense?

Reference Check: Compare to standard dosing guidelines

Patient Factors: Consider age, weight, organ function

Safety Guidelines

Before Calculation

• Verify patient weight is current and accurate
• Check drug concentration and expiration date
• Review patient allergies and contraindications
• Confirm indication and appropriateness of therapy

After Calculation

• Have calculation independently verified
• Use appropriate measuring devices
• Label syringes clearly with drug and concentration
• Document dose, route, and time of administration

Common Weight-Based Medications

Pediatric Medications

Acetaminophen (Tylenol)

Dose: 10-15 mg/kg every 4-6 hours
Max: 90 mg/kg/day or 4 g/day
Forms: 80 mg/mL, 160 mg/5mL suspension

Ibuprofen (Advil, Motrin)

Dose: 5-10 mg/kg every 6-8 hours
Max: 40 mg/kg/day
Forms: 40 mg/mL, 100 mg/5mL suspension

Amoxicillin

Dose: 20-40 mg/kg/day divided BID-TID
Max: 1 g per dose
Forms: 125 mg/5mL, 250 mg/5mL suspension

Adult Critical Care

Vancomycin

Loading: 25-30 mg/kg IV
Maintenance: 15-20 mg/kg every 8-12h
Monitor: Serum levels and kidney function

Propofol

Induction: 1-2.5 mg/kg IV
Maintenance: 25-200 mcg/kg/min
Concentration: 10 mg/mL

Norepinephrine

Start: 0.01-0.03 mcg/kg/min
Range: 0.05-2 mcg/kg/min
Concentration: 4 mg/250mL (16 mcg/mL)

Frequently Asked Questions

When should I use weight-based dosing vs. standard adult doses?

Use weight-based dosing for all pediatric patients, critical care medications, chemotherapy, and drugs with narrow therapeutic windows. Use standard adult doses for most routine oral medications in normal-weight adults. Always check drug references when unsure.

How do I handle obese patients in dose calculations?

For most medications, use actual body weight unless specifically indicated otherwise. Some drugs (like digoxin, chemotherapy) may require ideal body weight or adjusted body weight. Consult drug-specific references and institutional protocols for obese patients.

What should I do if my calculated dose seems too high or too low?

Stop and verify your calculation immediately. Check the patient weight, drug concentration, and calculation steps. Compare your result to standard dosing references. If the dose still seems inappropriate, consult with a pharmacist or physician before proceeding. Trust your clinical judgment.

How precise should my volume measurements be?

Use the most precise measuring device available. For volumes <1 mL, use tuberculin syringes marked in 0.01 mL increments. For 1-10 mL, use syringes marked in 0.1 mL. For larger volumes, use graduated cylinders or large syringes.Never estimate volumes - always use calibrated measuring devices.

What if the patient's weight is in pounds but the dose is in mg/kg?

Convert pounds to kilograms by dividing by 2.2 (or multiply by 0.454). For example: 154 lb ÷ 2.2 = 70 kg. Always convert to kg for medical calculations as most dosing guidelines use metric units. Some calculators include automatic conversion.

How do I calculate continuous infusion rates?

For infusions dosed in mcg/kg/min: Calculate total dose per minute, convert to hourly dose, then divide by concentration to get mL/hr. Example: 5 mcg/kg/min × 70 kg = 350 mcg/min = 21,000 mcg/hr = 21 mg/hr. If concentration is 4 mg/mL, infusion rate = 5.25 mL/hr.

What safety measures should I always follow?

Five Rights: Right patient, drug, dose, route, time. Always have calculations verified by another healthcare provider. Use only calibrated measuring devices. Check patient allergies and contraindications. Document all calculations and administration details. When in doubt, consult pharmacy or physician.