Calculate grams of a substance from total mixture mass and mass percent, or find the missing total mass or percent using common weight units.
| Percent to Grams | Grams to Percent |
|---|---|
| 0.1% of 100 g = 0.1 g | 0.2 g in 100 g = 0.2% |
| 0.25% of 100 g = 0.25 g | 0.4 g in 100 g = 0.4% |
| 0.5% of 100 g = 0.5 g | 0.8 g in 100 g = 0.8% |
| 1% of 100 g = 1 g | 3 g in 100 g = 3% |
| 2% of 100 g = 2 g | 6 g in 100 g = 6% |
| 5% of 100 g = 5 g | 15 g in 100 g = 15% |
| 10% of 100 g = 10 g | 25 g in 100 g = 25% |
| 25% of 100 g = 25 g | 50 g in 100 g = 50% |
| 50% of 100 g = 50 g | 75 g in 100 g = 75% |
| 75% of 100 g = 75 g | 100 g in 100 g = 100% |
| Formula: grams = total x % / 100. Assumes total mixture = 100 g. | |
| Percent to Grams | Grams to Percent |
|---|---|
| 10% of 1 kg = 100 g | 1 g in 1 kg = 0.1% |
| 12.5% of 1 kg = 125 g | 2.5 g in 1 kg = 0.25% |
| 15% of 1 kg = 150 g | 5 g in 1 kg = 0.5% |
| 20% of 1 kg = 200 g | 10 g in 1 kg = 1% |
| 25% of 1 kg = 250 g | 25 g in 1 kg = 2.5% |
| 33.3% of 1 kg = 333 g | 50 g in 1 kg = 5% |
| 50% of 1 kg = 500 g | 100 g in 1 kg = 10% |
| 75% of 1 kg = 750 g | 250 g in 1 kg = 25% |
| Formula: grams = total x % / 100. Assumes total mixture = 1 kg. | |
| Substance | Solute | Typical w/w% | g per 1 kg mixture |
|---|---|---|---|
| Seawater | Dissolved salts (NaCl dominant) | 3.5% | 35 g |
| Normal saline (IV) | NaCl | 0.9% | 9 g |
| Sports drink (Gatorade-type) | Carbohydrates | 6-8% | 60-80 g |
| Household vinegar | Acetic acid | 4-5% | 40-50 g |
| Household bleach | Sodium hypochlorite (NaOCl) | 3-8% | 30-80 g |
| Drugstore hydrogen peroxide | H2O2 | 3% | 30 g |
| Whole cow milk | Fat | 3.25-3.5% | 32.5-35 g |
| Blood plasma (human) | Total protein | 6-8% | 60-80 g |
| Retinol cosmetic cream | Retinol | 0.025-1% | 0.25-10 g |
| OTC saline eye drops | NaCl | 0.9% | 9 g |
| All values are mass of solute per total mass of mixture (w/w%). Values are typical ranges; formulations vary. | |||
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Percent to Grams Formula
The formula below calculates the mass in grams of a substance given its mass percent and total mixture mass.
G = TM * POM / 100
- G = grams of the substance
- TM = total mass of the mixture (grams)
- POM = percent of mass the substance represents (%)
w/w% vs w/v%: A Key Distinction
Mass percent comes in two common forms that are frequently confused. Weight-by-weight percent (w/w%) expresses grams of solute per 100 grams of total mixture, which is what this calculator uses. Weight-by-volume percent (w/v%) expresses grams of solute per 100 mL of solution, which is standard in pharmacy and clinical settings.
For dilute water-based solutions at room temperature, where solution density is near 1 g/mL, the two values are nearly identical. The difference grows with concentrated solutions or non-aqueous solvents. A 40% ethanol solution by mass is approximately 49% ethanol by volume, because ethanol (0.789 g/mL) is less dense than water. Always confirm which convention a label or protocol uses before calculating.
Worked Example
Household bleach is labeled 5.25% sodium hypochlorite (NaOCl). A spray bottle holds 750 g of bleach solution. How many grams of NaOCl does it contain?
G = 750 g x 5.25 / 100 = 39.4 g NaOCl
Conversely, to find what percentage 9 g of NaCl represents in a 1,000 g saline bag: POM = (9 / 1000) x 100 = 0.9% NaCl, the standard physiological saline concentration used in IV fluids and eye drops.
