ProReckoner provides free clinical calculators trusted by nurses in Australia and worldwide. Every tool is built around standard nursing formulas — from IV drip rate calculations and drug dosing to NEWS2 early warning scoring, fluid balance tracking, FiO₂ estimation, Glasgow Coma Scale, paediatric weight-based dosing and BMI assessment. All calculations are instant, work on any device, and support both metric and imperial units. No login or app download required.
IV & Fluids
3 toolsIV Drip Rate (Gravity)
Drops per minute for gravity-fed infusions. Select your giving set drop factor.
gtt/min = Volume (mL) × Drop factor ÷ (Time hrs × 60)
Example: 1500 mL, 10 hrs, 20 gtt/mL = 1500×20÷600 = 50 gtt/min
Infusion Time & Volume
Three-way calculator — find time remaining, total volume or flow rate from any two known values.
Volume = Rate × Time
Rate = Volume ÷ Time
Time = Volume ÷ Rate
Example: 2000 mL at 160 mL/hr → 2000÷160 = 12.5 hrs
Infusion Pump Rate (mL/hr)
mL/hr pump setting from volume and time ordered. Includes blood product 4-hour safety alert.
mL/hr = Volume ÷ Time (hours)
Blood products must complete within 4 hours of issue per international guidelines. Label bag with start time.
Medication
2 toolsTablet & Oral Liquid Dose
How many tablets or mL to give. SR ÷ SS × Volume — works for tablets, liquids and injections.
Amount = (SR ÷ SS) × Stock volume
Example: SR 750 mg, SS 500 mg tablet → (750÷500)×1 = 1.5 tabletsLiquid: SR 250 mg, SS 125 mg/5mL → (250÷125)×5 = 10 mL
Drug Dose by Weight (mg/kg)
Total dose and volume from a weight-based order. Supports IV, IM and oral routes. Auto-converts lb→kg.
Total mg = Weight (kg) × Dose (mg/kg)
Volume (mL) = Total mg ÷ Concentration (mg/mL)
Example: 70 kg patient, 15 mg/kg, stock 50 mg/mLTotal = 1050 mg · Volume = 21 mL
Dilution & Reconstitution
2 toolsDrug Dilution Calculator
How much diluent to add to reach a target concentration. Common for morphine, heparin and potassium infusions.
Stock drawn = Drug required ÷ Stock concentration
Diluent = Final volume − Stock drawn
Example (morphine): 30 mg needed, stock 10 mg/mL, final 30 mLStock = 3 mL · Diluent = 27 mL saline
Reconstitution Calculator
Volume to draw up after adding diluent to a powdered vial. Enter displacement volume if stated on the label.
Concentration = Vial mg ÷ (Diluent + Displacement)
Volume to give = Ordered dose ÷ Concentration
Conversion
1 toolUnit Converter
Convert between common clinical units — weight, mass, volume, length and temperature.
× 1000: g→mg · mg→mcg · L→mL
÷ 1000: mg→g · mcg→mg · mL→L
lb→kg: × 0.4536 · °C→°F: ×9/5+32
Normal body temp: 36.1–37.2°C (97–99°F)
Assessment
2 toolsBMI & Weight Status
BMI and clinical weight category per WHO guidelines. Includes adjusted ranges for older adults (65+).
BMI = Weight (kg) ÷ Height (m)²
For adults 65+, healthy BMI is 22–27 — higher than standard, as low BMI in older adults increases mortality risk.
Glasgow Coma Scale (GCS)
Total GCS score with severity classification. Select the best response observed for each component (Eye, Verbal, Motor).
GCS = Eye (1–4) + Verbal (1–5) + Motor (1–6)
Severity classification:15 = Normal · 13–14 = Minor · 9–12 = Moderate · ≤8 = Severe (airway risk)
NEWS2 Score
National Early Warning Score 2 — the standard deterioration scoring tool used across Australia, UK and NZ. Scores 6 physiological parameters plus O₂ supplementation.
NEWS2 = RR + SpO₂ + Air/O₂ + SBP + HR + Consciousness + Temp
Clinical thresholds: 0 = routine monitoring · 1–4 = low (assess 4–6 hourly) · 5–6 or any single 3 = medium (urgent review) · ≥7 = high (MET/RRT call)SpO₂ Scale 2 applies only to patients with confirmed hypercapnic respiratory failure (e.g. COPD) with a prescribed target of 88–92%.
O₂ Flow Rate / FiO₂ Calculator
Convert between O₂ flow rate (L/min) and estimated FiO₂ for nasal cannula, simple mask, NRB and Venturi. Also finds the right device for a target FiO₂.
Nasal cannula: 1L=24% · 2L=28% · 4L=36% · 6L=44%
Simple mask: 5–6L=35–40% · 8–10L=50–60%
NRB mask: 10–15L=80–95% · Venturi: fixed FiO₂ per barrel colour
HFNC: set FiO₂ 21–100% · BVM with O₂: ~100%
SpO₂ target: 94–98% (most adults) · 88–92% (COPD/hypercapnic)
Fluid Balance
1 toolFluid Balance / Intake & Output
Running 24-hour fluid balance tracker. Add inputs (IV fluids, oral, NGT) and outputs (urine, drain, vomit) individually. Tap ✕ to remove any entry. Flags fluid overload and deficit.
Intake: ~2000–2500 mL · Output: ~2000–2500 mL · Balance: ±200 mL
Insensible losses: ~500–800 mL/day (respiration, skin) — not measurable
Urine output targets: ≥0.5 mL/kg/hr adult · ≥1 mL/kg/hr child
Flags: Positive >2000 mL — fluid overload risk · Negative >500 mL — dehydration risk
Paediatric
1 toolPaediatric Drug Dose Calculator
Weight-based dosing for neonates, infants and children. Enter the mg/kg order, weight and stock concentration to get the volume to give. Supports dose ranges (min–max). Metric and Imperial.
Total dose (mg) = Weight (kg) × Dose (mg/kg)
Volume (mL) = Total dose ÷ Concentration (mg/mL)
Example (paracetamol): 20 kg child, 15 mg/kg oral, stock 120 mg/5 mL (24 mg/mL)Total = 300 mg · Volume = 12.5 mL
Shift & Time
2 toolsShift Hours & Overtime
Total hours worked with break deduction and overtime flag. Handles overnight shifts.
Hours = (End − Start) − (Break ÷ 60)
Overnight example: start 22:00, finish 06:30 → enter end as 30.5
Military Time Converter
Convert between 12-hour AM/PM and 24-hour military time. Essential for correct medication documentation.
PM→24h: add 1200 (except 12PM=1200, 12AM=0000)