# Scruples to Grains (s ap to gr)

Source: https://www.unitconvertercalculator.com/weight/scruples-to-grains/

**1 s ap = 20 gr**

One scruple equals exactly 20 grains. This is a defining relationship within the apothecary weight system, as clean and fundamental as 24 grains per pennyweight in the troy system. The scruple was designed to contain precisely 20 grains, making subdivision into halves, quarters, fifths, and tenths straightforward for pharmaceutical compounding.

## Formula

Apply the conversion factor

## Conversion Table

| Scruples (s ap) | Grains (gr) |
|---|---|
| 0.25 s ap | 5 gr |
| 0.5 s ap | 10 gr |
| 1 s ap | 20 gr |
| 3 s ap | 60 gr |
| 5 s ap | 100 gr |
| 10 s ap | 200 gr |
| 20 s ap | 400 gr |
| 24 s ap | 480 gr |
| 50 s ap | 1000 gr |
| 100 s ap | 2000 gr |
| 200 s ap | 4000 gr |
| 288 s ap | 5760 gr |
| 500 s ap | 10000 gr |
| 1000 s ap | 20000 gr |

## Units

### Scruple (s ap)

An apothecary scruple equals 20 grains or 1/3 of a dram apothecary (1.2959782 grams). A historical pharmaceutical unit largely replaced by metric measurements.

### Grain (gr)

A grain is a unit of mass equal to exactly 64.79891 milligrams. It is the same in the avoirdupois, troy, and apothecaries' systems, derived from the 1959 international agreement defining the pound as exactly 0.45359237 kilograms.

## Background

When 18th-century physicians wrote prescriptions in scruples and pharmacists filled them using grain weights on balance scales, the 20-grain scruple was the essential bridge between prescription notation and physical measurement. A prescription for 'half a scruple' meant exactly 10 grains, and a 'quarter scruple' meant 5 grains, both whole numbers that pharmacists could weigh precisely.

## Good to Know

The 20-grain scruple, like the 24-grain pennyweight, reflects medieval measurement design philosophy: choose numbers that divide cleanly into many fractions. Pharmacists needed halves, quarters, fifths, and tenths of a scruple more often than thirds or sixths, making 20 the ideal base. This practical numerology shaped pharmaceutical dosing for over 500 years, until the milligram rendered these divisions unnecessary.

## FAQ

### How many grains are in one scruple?

There are exactly 20 grains in one scruple. This is a definitional relationship within the apothecary weight system, established centuries ago and used throughout the history of Western pharmacy.

### Why 20 grains per scruple?

Twenty was chosen because it divides evenly into halves (10), quarters (5), fifths (4), and tenths (2), all useful fractions for pharmaceutical dosing. This divisibility made the scruple practical for pharmacists who subdivided doses using balance scales and grain weights.

### Is the grain in the scruple the same as in the troy system?

Yes, the grain is identical across the apothecary, troy, and avoirdupois systems at exactly 64.79891 milligrams. The grain is the one universal unit shared by all three English weight traditions.

## Non-Frequently Asked Questions

### If I have no scruples, do I also have no grains?

In the apothecary sense, zero scruples equals zero grains, which is mathematically true and pharmaceutically useless. In the moral sense, having no scruples leaves you with an undetermined number of grains, since ethical weight and physical weight unfortunately do not correlate. Many unscrupulous individuals are quite heavy.

### Is 20 grains per scruple a better number than 24 grains per pennyweight?

Both are excellent choices for pre-calculator arithmetic. Twenty divides by 2, 4, 5, and 10; twenty-four divides by 2, 3, 4, 6, 8, and 12. The pennyweight has more factors, but the scruple has rounder ones. Pharmacists preferred 20 because dose fractions in fifths and tenths were common in their work; goldsmiths preferred 24 because thirds and sixths mattered in metal alloying.

### Could I weigh 20 actual grain seeds and get one scruple?

You would get an approximation, not an exact scruple. The grain weight unit (64.8 mg) was standardized long ago against a physical reference, not against actual seeds. Modern barley grains vary from about 50 to 80 mg each, so 20 grains of barley would give you roughly 1 to 1.6 grams versus the scruple's precise 1.296 grams. Close, but not pharmacy-grade precision.

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## See Also

- [Grains to Scruples](https://www.unitconvertercalculator.com/weight/grains-to-scruples/)