药物剂量计算器 — 基于体重的 mg/kg 给药
Use this free dosage calculator to compute weight-based drug doses using the mg/kg method. Enter the patient weight, prescribed dose per kilogram, and dosing frequency. Optionally enter the medication concentration to calculate the volume in mL per dose. This tool is for educational purposes only— always verify calculated doses with a licensed healthcare professional before administration.
Weight-Based Dosage Calculator
Enter the patient weight, prescribed dose per kilogram, dosing frequency, and optional concentration to calculate the total and per-administration dose.
e.g. 1 = once daily, 2 = twice daily (BID), 3 = three times daily (TID), 4 = four times daily (QID)
Enter the liquid medication concentration to calculate volume per dose (mL).
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常见问题
剂量计算器是如何工作的？
剂量计算器根据患者体重和药物推荐剂量（mg/kg 或 mcg/kg）计算个体化用药量。公式为：剂量 = 体重(kg) × 剂量(mg/kg)。可同时换算为液体制剂的毫升数。
为什么剂量是按体重计算的？
按体重计算剂量可以确保药物浓度在体内达到治疗效果所需的水平。对于儿童和体重差异较大的成人，这种个体化计算尤为重要，可避免用药不足或过量。
我可以使用这个计算器来计算儿童剂量吗？
本计算器适用于儿科剂量计算。儿童药物剂量通常以 mg/kg 表示，并设有最大剂量上限（不超过成人剂量）。请务必参考儿科药物手册并咨询医疗专业人员。
什么是最大剂量？
最大剂量是指即使按体重计算结果更高，也不应超过的剂量上限。通常以成人标准剂量为上限，防止对大体重患者（尤其是儿童）过度给药。
About the Dosage Calculator
Weight-Based Dosing Formula
Weight-based dosing (mg/kg) is the standard approach for calculating drug doses in pediatric patients and in adults where body size significantly affects drug distribution, metabolism, or toxicity. The formula ensures the dose is proportional to the patient's body mass.
Daily Dose (mg) = Weight (kg) × Dose per kg (mg/kg)
Dose per Administration (mg) = Daily Dose / Frequency (times/day)
Volume per Dose (mL) = Dose per Administration / Concentration (mg/mL)
Where:
- Weight (kg)— Patient body weight in kilograms. Pounds are automatically converted using: kg = lbs × 0.453592
- Dose per kg (mg/kg)— The prescribed dose in milligrams per kilogram of body weight, as specified by clinical guidelines or a prescribing physician
- Frequency— Number of administrations per 24-hour period (e.g., 1 for once daily, 2 for BID, 3 for TID, 4 for QID)
- Concentration (mg/mL)— Optional. The strength of a liquid formulation, used to calculate the volume (in mL) to draw up or administer
Always use actual body weight unless otherwise directed. In some cases (e.g., obese patients or certain chemotherapy regimens), adjusted body weight (ABW) or ideal body weight (IBW) may be specified by the prescriber.
Common Pediatric Doses
The following table lists approximate weight-based doses for commonly used medications in pediatric patients. These are general guidelines only — always verify with current clinical references (e.g., Lexicomp, Micromedex, or the BNF for Children).
| Drug | Typical Dose | Frequency | Indication |
|---|---|---|---|
| Acetaminophen (Paracetamol) | 10–15 mg/kg | Every 4–6 hours (max 5×/day) | Pain, fever |
| Ibuprofen | 5–10 mg/kg | Every 6–8 hours | Pain, fever, inflammation |
| Amoxicillin | 25–45 mg/kg/day | Divided every 8–12 hours | Bacterial infections |
| Azithromycin | 10 mg/kg (day 1), then 5 mg/kg | Once daily for 5 days | Respiratory infections |
| Prednisolone | 1–2 mg/kg/day | Once or twice daily | Asthma, croup, inflammation |
| Ceftriaxone (IV) | 50–100 mg/kg/day | Once daily | Serious bacterial infections |
| Ondansetron | 0.1–0.15 mg/kg | Every 8 hours (as needed) | Nausea and vomiting |
Note: Maximum dose caps apply to all weight-based calculations. For example, acetaminophen is typically capped at 1,000 mg per dose regardless of weight. Always check product monographs and clinical guidelines for dose limits.
Frequency Guide
Medical dosing frequencies use standardized abbreviations derived from Latin. The following table maps common frequency terms to the number of daily administrations:
| Abbreviation | Latin Origin | Meaning | Times/Day |
|---|---|---|---|
| QD / OD | Quaque die | Once daily | 1 |
| BID | Bis in die | Twice daily | 2 |
| TID | Ter in die | Three times daily | 3 |
| QID | Quater in die | Four times daily | 4 |
| Q4H | Quaque 4 hora | Every 4 hours | 6 |
| Q6H | Quaque 6 hora | Every 6 hours | 4 |
| Q8H | Quaque 8 hora | Every 8 hours | 3 |
| Q12H | Quaque 12 hora | Every 12 hours | 2 |
Enter the numeric value (e.g., “2” for BID, “3” for TID) into the frequency field in the calculator above.
Safety Checks
Weight-based dosage calculations require careful attention to safety. Before administering any medication, verify the following:
- Maximum Dose Limits— Most drugs have a maximum single dose and a maximum daily dose. For example, ibuprofen is typically capped at 400–600 mg per dose and 2,400 mg/day in adults, regardless of weight. Always check the product monograph.
- Correct Weight Used— Use the patient's current actual body weight in kilograms. In obese patients, some drugs (e.g., aminoglycosides, vancomycin) require adjusted body weight. The prescriber should specify.
- Concentration Verification— Liquid medications are available in multiple concentrations (e.g., acetaminophen 160 mg/5 mL vs. 500 mg/5 mL). Always confirm which concentration is being used before calculating volume.
- Renal and Hepatic Impairment— Kidney or liver dysfunction may require dose reduction or extended dosing intervals. Consult a pharmacist or clinical guidelines for renally-adjusted dosing.
- Drug Interactions— Multiple concurrent medications may interact. Use a drug interaction checker (e.g., Drugs.com, Lexicomp) or consult a pharmacist.
- Allergy and Contraindication Review— Check for documented allergies and contraindications before prescribing or administering any drug.
- Double-Check Calculations— Always have a second person independently verify high-alert medication calculations (e.g., chemotherapy, anticoagulants, insulin) before administration.
Ten-Fold Errors: A common and dangerous calculation error involves a decimal point misplacement, resulting in doses that are 10 times too high or too low. Always double-check your arithmetic and verify units (mg vs. mcg, mL vs. L).
Medical Disclaimer
This dosage calculator and the information on this page are provided for educational and informational purposes only. The results are mathematical calculations and do not constitute medical advice. Drug dosing is highly individualized and must account for the patient's age, weight, renal and hepatic function, concurrent medications, allergies, clinical indication, and other factors. Never administer a medication based solely on the output of this calculator. Always verify calculated doses with a licensed pharmacist, physician, or nurse practitioner before administration. If you are a patient or caregiver, consult your healthcare provider for personalized dosing guidance.