Weech formulas
The Weech formulas are used to estimate expected height and weight in children based on age. Here's a quick summary from memory:
Height:
- Age 2-12 years: Height (cm) = 2.5 x Age (years) + 30 (in inches: Age x 2.5 + 30... actually the classic form is below)
Weight:
- Age 1-6 years: Weight (kg) = Age + 9...
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Weech formulas pediatrics height weight age
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The library doesn't have a dedicated Weech formula entry, but the web search returned comprehensive results. Here is the full breakdown:
Weech Formulas
Named after Dr. A.A. Weech, these are quick bedside/exam formulas to estimate expected anthropometric parameters in children aged 3 months to 12 years. They are widely used in pediatrics, particularly in growth assessment and nutritional screening.
1. Expected Weight
| Age Group | Formula |
|---|---|
| 3-12 months | Weight (kg) = (Age in months + 9) / 2 |
| 1-6 years | Weight (kg) = (Age in years × 2) + 8 |
| 7-12 years | Weight (kg) = (Age in years × 7 - 5) / 2 |
Examples:
- 6-month-old: (6 + 9) / 2 = 7.5 kg
- 3-year-old: (3 × 2) + 8 = 14 kg
- 10-year-old: (10 × 7 - 5) / 2 = 32.5 kg
2. Expected Height
For 2-12 years:
Height (cm) = (Age in years × 6) + 77
Examples:
- 3-year-old: (3 × 6) + 77 = 95 cm
- 7-year-old: (7 × 6) + 77 = 119 cm
3. Expected Head Circumference
| Age | Formula |
|---|---|
| < 1 year | HC (cm) = (Height in cm / 2) + 10 |
| > 1 year | HC (cm) = (Age in years / 2) + 33 |
Alternatively recalled as:
- At birth: ~34 cm
- At 1 year: ~47 cm
Quick Reference - Weight Milestones
| Age | Weight relative to birth weight (X) |
|---|---|
| Birth | X |
| 5 months | 2X (doubles) |
| 1 year | 3X (triples) |
| 2 years | 4X (quadruples) |
Clinical Use
These formulas are used to:
- Rapidly screen for underweight and stunting without growth charts
- Calculate drug dosages based on ideal body weight in children
- Identify malnutrition at the bedside
A 2010 study (PMID: 21744764) validated Weech's formulas as a sensitive tool for detecting underweight and stunting in children aged 12-59 months.
Note: The 1-6 year formula (Age × 2 + 8) is the most commonly tested in exams (NEET PG, USMLE Step 1). For children 7-12 years, some sources simplify to Age × 3 as an approximation.
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