Medication dosing errors kill people. According to the FDA, they account for roughly 37% of all reported medication errors. We decided to build something about it.
At MDTools.org, we created a suite of free, open-source drug dosing calculators — no signup, no ads, no paywall. Every tool loads in under 1 second on any device. Here's our technical approach and what we built.
The Architecture: Zero Dependencies
Every calculator is vanilla JavaScript. No React. No Vue. No build step. Each page is a single HTML file with inline CSS and JS. The result:
- < 50KB per page (including all CSS/JS)
- < 1 second load time on 3G connections
- Zero external dependencies to break or slow things down
- Works offline once cached
Drug Dosing Calculators
Here's what we built, each implementing formulas directly from published clinical guidelines:
Anticoagulants
- Heparin Dosing — Weight-based protocols with aPTT-guided adjustments per 2012 ACCP guidelines
- Warfarin Dose Calculator — INR-based adjustment following the Coumacare algorithm
- Vancomycin AUC Calculator — AUC/MIC-guided dosing per 2020 ASHP/IDSA consensus
Endocrine & Metabolic
- Insulin Dose Calculator — Basal-bolus and correction factor calculations
- Semaglutide Dosing — Ozempic/Wegovy titration schedules with timing guidance
Anesthesia & Pain
- Ketamine Dosing — Procedural sedation by route (IV, IM, intranasal)
- Lidocaine Dosing — Max safe dose with/without epinephrine
Pediatrics
- Amoxicillin Pediatric Dosing — Weight-based for otitis media, strep, UTI, pneumonia
- Infant Tylenol Dosing — Acetaminophen by weight, multiple formulations
- Pediatric Ibuprofen — Weight-based with formulation selection
Supporting Clinical Tools
Dosing calculators don't exist in isolation. Clinicians need these alongside:
- Creatinine Clearance — Cockcroft-Gault for renal dose adjustments
- eGFR Calculator — CKD-EPI 2021 equation
- BSA Calculator — Body surface area for chemo dosing
- IV Drip Rate — Drops/min and mL/hr calculations
- Dose by Weight — Generic weight-based calculator
- BMI Calculator — With obesity staging
Pharmacy Tools
We expanded into pharmacy workflow calculators:
- Prescription Refill Calculator — Next refill dates
- Day Supply Calculator — For insurance billing
- Medication Timing — Daily schedule generator
- Pill Count — Dispensing verification
Lab Reference Values
We also built evidence-based lab reference pages grounded in Tietz Clinical Chemistry:
CRP · Bilirubin · Potassium · Sodium · Creatinine · Albumin · Calcium · Chloride · ALP · BNP
The Citation Standard
Every formula on MDTools cites its source. Every page has a "Formula last verified" date. We link to original guidelines (ACCP, ASHP/IDSA, KDIGO, etc.) because transparency builds trust.
International Access
We offer a complete German localization covering all 100+ tools. Drug names are localized (Vyvanse → Elvanse, Accutane → Aknenormin).
Open Source
Everything is MIT licensed on GitHub. The formula library is at medical-calculator-formulas. We also maintain an awesome-medical-tools list.
All tools: mdtools.org — free, forever, for everyone.
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