Grain to Gram Converter
Precise weight conversion between grains and grams
Quick Convert
Conversion Tables
Common Grain to Gram Conversions
| Grains (gr) | Grams (g) | Milligrams (mg) |
|---|---|---|
| 1 gr | 0.0648 g | 64.80 mg |
| 5 gr | 0.3240 g | 324.0 mg |
| 10 gr | 0.6480 g | 648.0 mg |
| 15 gr | 0.9720 g | 972.0 mg |
| 20 gr | 1.296 g | 1,296 mg |
| 50 gr | 3.240 g | 3,240 mg |
| 100 gr | 6.480 g | 6,480 mg |
| 250 gr | 16.20 g | 16,200 mg |
| 500 gr | 32.40 g | 32,400 mg |
| 1,000 gr | 64.80 g | 64,799 mg |
Gram to Grain Conversions
| Grams (g) | Grains (gr) |
|---|---|
| 0.1 g | 1.543 gr |
| 0.5 g | 7.716 gr |
| 1 g | 15.432 gr |
| 5 g | 77.162 gr |
| 10 g | 154.324 gr |
| 25 g | 385.809 gr |
| 50 g | 771.618 gr |
| 100 g | 1,543.236 gr |
Conversion Formula & Method
Grain to Gram:
Grams = Grains × 0.06479891
Gram to Grain:
Grains = Grams × 15.4323584
Step-by-Step Conversion
To convert grains to grams:
- Take the number of grains you want to convert
- Multiply by 0.06479891 (the conversion factor)
- The result is your value in grams
- Example: 100 gr × 0.06479891 = 6.480 g
To convert grams to grains:
- Take the number of grams you want to convert
- Multiply by 15.4323584 (the reverse conversion factor)
- The result is your value in grains
- Example: 10 g × 15.4323584 = 154.324 gr
Historical Background
The grain is one of the oldest units of mass measurement, with origins in ancient civilisations. In Britain, the grain became the legal foundation of traditional weight systems and is the only unit equal throughout the troy, avoirdupois, and apothecaries’ systems.
Originally based on the weight of a single grain of barley, the unit was formally standardised in thirteenth-century England. A royal decree stated that “an English Penny, which is called the Sterling, round without clipping, shall weigh Thirty-two Grains of Wheat dry in the midst of the Ear.”
The Imperial Weights and Measures Act 1824 brought further standardisation, defining the avoirdupois pound as exactly 7,000 grains. Following the International Yard and Pound Agreement of 1 July 1959, the grain was precisely defined as 64.79891 milligrams (0.06479891 grams) in terms of SI units.
Modern Applications
Whilst the grain is no longer commonly used for everyday measurements in the UK, it remains relevant in several specialised fields:
Pharmaceuticals
Historically used in the apothecaries’ system for measuring medicines and compounds
Precious Metals
Related to the troy system still used for weighing gold, silver, and gemstones
Archery
Arrow weights are often specified in grains in traditional archery
Reloading
Powder charges and bullet weights measured in grains for firearms
Unit Comparison
Relationship to Other Units
| Unit | Equivalent to 1 Grain | Context |
|---|---|---|
| Milligrams | 64.79891 mg | Metric system (SI) |
| Grams | 0.06479891 g | Metric system (SI) |
| Ounces (avoirdupois) | 0.00228571 oz | Imperial system |
| Pounds (avoirdupois) | 0.000142857 lb | Imperial system (1 lb = 7,000 gr) |
| Carats (metric) | 0.32399 ct | Gemstone measurement |
Did you know? One gram equals approximately 15.43 grains. This means a standard UK 5-pence coin (weighing 3.25 g) is equivalent to about 50.2 grains.
Frequently Asked Questions
What is the exact conversion ratio between grains and grams?
One grain is exactly equal to 64.79891 milligrams, or 0.06479891 grams. Conversely, one gram equals 15.4323584 grains. This conversion has been internationally standardised since 1959.
Why is the grain still used in some industries?
The grain remains in use primarily for historical and practical reasons. In fields like precious metals trading, pharmaceuticals (particularly traditional compounding), and certain sporting activities, the grain provides a familiar and convenient unit that has been used for centuries. The troy system, which includes grains, is still legally recognised for weighing precious metals in the UK.
Is the grain used differently in the UK versus other countries?
No, the grain is defined identically worldwide since the 1959 International Yard and Pound Agreement. Whether in the UK, United States, or elsewhere, one grain always equals exactly 64.79891 milligrams. However, the contexts in which it’s used may vary between countries.
How accurate do I need to be when converting grains to grams?
For most everyday purposes, rounding to four decimal places (0.0648 g per grain) provides sufficient accuracy. However, in scientific, pharmaceutical, or precious metals applications, you should use the full conversion factor (0.06479891) to maintain precision.
Are grains part of the metric or imperial system?
Grains are part of the imperial system of measurements, though they’re unique in being used across multiple weight systems (troy, avoirdupois, and apothecaries’). Whilst the UK has largely adopted the metric system for most measurements, grains remain legally defined and still appear in certain specialised contexts.
What’s the difference between troy grains and avoirdupois grains?
There is no difference—the grain is the same in both systems. One grain equals 64.79891 milligrams whether you’re working with troy weights (used for precious metals) or avoirdupois weights (used for general purposes). This uniformity makes the grain unique amongst traditional British units.
Can I use this converter for pharmaceutical measurements?
Whilst this converter provides accurate conversions, pharmaceutical dosing requires professional oversight. The apothecaries’ system historically used grains for medicine, but modern pharmaceutical practice in the UK predominantly uses metric measurements. Always consult a qualified healthcare professional for any medicine-related measurements.
Why was the grain originally based on barley?
In medieval England, barley grains provided a readily available and relatively uniform standard for small weights. The system stated that one grain equalled the weight of a single grain of barley “from the middle of the ear.” Whilst actual barley grains vary in weight, this provided a practical starting point for standardisation, which was later refined to the exact metric equivalent we use today.