People type this into search as a protein calculator, in grams per day.
The protein intake calculator answers with two published ranges. The headline is the adult RDA. The lines under it are the AMDR, which is a share of the calories you type. Both come from the National Academies. Neither one is a meal plan.
Two formulas, one card
The National Academies protein DRI sets the adult RDA at 0.8 g of protein per kilogram of body weight. The same tables set the adult AMDR at 10 to 35 percent of energy.
The FDA calorie page counts protein at 4 kcal per gram. The calculator uses that factor to turn the percent into grams.
RDA grams = 0.8 × kilograms
AMDR low = calories × 0.10 ÷ 4
AMDR high = calories × 0.35 ÷ 4
The gram lines are rounded to the nearest gram. A half gram rounds away from zero, so 45.6 g displays as 46 g and 45.5 g would display as 46 g. The weight line on a US visit is pounds. The site multiplies kilograms by 2.204622622 and keeps one decimal. The formula itself still multiplies kilograms. Type kilograms in the weight field. The suffix on that field is kg.
The assumptions on the calculator name the reference bodies behind the RDA tables. 0.8 × 70 kg is 56 g. 0.8 × 57 kg is 45.6 g, which displays as 46 g.
Fig 1
Weight sets the RDA, calories set the band
Both numbers can sit on the same card
The RDA is 0.8 g times kilograms. The AMDR turns 10 percent and 35 percent of the calories into grams at 4 kcal per gram.
Leave calories at 0 when you only want the RDA. The AMDR lines stay off the card until calories are above 0. A wrong calorie guess moves only the band. The RDA still follows the weight.
The calorie figure, if you want one from height, age, and a PAL, comes from the daily calorie calculator and the calorie post. Body weight as a BMI screen is the BMI post. Fluid is a different DRI, covered in the water post.
Pregnancy, illness, and hard training can raise the useful amount. The 0.8 g per kg figure is the adult RDA for healthy adults. Ask a clinician before you treat the card as a diet.
Example 1: the default, 70 kg and 2,000 kcal
- weight: 70 kg
- calories: 2,000 kcal
RDA: 0.8 × 70 = 56 g
AMDR low: 2,000 × 0.10 = 200 kcal, and 200 ÷ 4 = 50 g
AMDR high: 2,000 × 0.35 = 700 kcal, and 700 ÷ 4 = 175 g
Weight on the card: 70 × 2.204622622 = 154.323, displayed as 154.3 lb
56 g of protein is 56 × 4 = 224 kcal. That is 224 ÷ 2,000 = 11.2 percent of this day. The RDA sits 6 g above the 10 percent line, and 119 g under the 35 percent line.
Calculator result
Protein intake target
- Weight
- 70 kg
- Daily calories
- 2000 kcal
56 g
National Academies adult protein RDA
- Weight used
- 154.3 lb
- RDA rate
- 0.8 g per kg
- AMDR low (10% of calories)
- 50 g
- AMDR high (35% of calories)
- 175 g
- Calories used
- 2,000 kcal
Fig 2 · 1/2
Where 56 g sits inside 2,000 kcal
FDA counts protein at 4 kcal per gram
RDA, 56 g
224 kcal
Rest of the day
1,776 kcal
The 10 percent line is 200 kcal, which is 50 g.
The RDA is 224 kcal. The other 1,776 kcal are the rest of the day.
Example 2: 80 kg and 2,400 kcal
Change both fields. This is the worked case on the calculator’s own guide.
RDA: 0.8 × 80 = 64 g
AMDR: 2,400 × 0.10 ÷ 4 = 60 g, and 2,400 × 0.35 ÷ 4 = 210 g
Weight on the card: 176.4 lb
The RDA is 4 g above the AMDR floor. At Example 1 the gap was 6 g. A heavier body and a higher calorie line moved both numbers, and the gap got smaller. Example 6 holds the weight still so you can see the calorie line do that on its own.
Calculator result
Protein intake target
- Weight
- 80 kg
- Daily calories
- 2400 kcal
64 g
National Academies adult protein RDA
- Weight used
- 176.4 lb
- RDA rate
- 0.8 g per kg
- AMDR low (10% of calories)
- 60 g
- AMDR high (35% of calories)
- 210 g
- Calories used
- 2,400 kcal
Example 3: the 57 kg reference weight
The calculator’s assumptions use 57 kg as the female reference weight in the RDA tables.
- weight: 57 kg
- calories: 1,800 kcal
RDA: 0.8 × 57 = 45.6, displayed as 46 g
AMDR low: 1,800 × 0.10 ÷ 4 = 45 g
AMDR high: 1,800 × 0.35 = 630, and 630 ÷ 4 = 157.5, displayed as 158 g
Weight on the card: 57 × 2.204622622 = 125.663, displayed as 125.7 lb
The displayed RDA is 1 g above the AMDR floor. The unrounded RDA is 45.6 g, so the true gap is 0.6 g. One gram of the card’s gap is the rounding from 45.6 to 46.
Calculator result
Protein intake target
- Weight
- 57 kg
- Daily calories
- 1800 kcal
46 g
National Academies adult protein RDA
- Weight used
- 125.7 lb
- RDA rate
- 0.8 g per kg
- AMDR low (10% of calories)
- 45 g
- AMDR high (35% of calories)
- 158 g
- Calories used
- 1,800 kcal
Example 4: a smaller adult and a larger one
45 kg and 1,400 kcal.
RDA: 0.8 × 45 = 36 g
AMDR low: 1,400 × 0.10 ÷ 4 = 35 g. The high end is 1,400 × 0.35 ÷ 4, which is 122.5 in exact arithmetic. The value the formatter sees is a hair under 122.5, so the card shows 122 g rather than 123.
Weight on the card: 99.2 lb
The RDA is 1 g above the floor. 36 × 4 = 144 kcal, which is 144 ÷ 1,400 = 10.3 percent of this day.
110 kg and 3,000 kcal.
RDA: 0.8 × 110 = 88 g
AMDR low: 3,000 × 0.10 ÷ 4 = 75 g
AMDR high: 3,000 × 0.35 = 1,050, and 1,050 ÷ 4 = 262.5, displayed as 263 g
Weight on the card: 242.5 lb
Here the RDA is 13 g above the floor. The high end is 263 − 88 = 175 g above the RDA. The band is wide on every row in this post. The RDA is one gram target. The AMDR is the range of calorie shares the DRI tables allow for protein.
Example 5: what if I change only the weight
Calories stay at 2,000. The AMDR stays 50 g to 175 g on every row, because those grams come from the calories. Each extra kilogram adds 0.8 g to the RDA. Ten kilograms add 8 g.
| Weight | On the card | RDA | AMDR at 2,000 kcal |
|---|---|---|---|
| 50 kg | 110.2 lb | 40 g | 50 to 175 g |
| 60 kg | 132.3 lb | 48 g | 50 to 175 g |
| 63 kg | 138.9 lb | 50 g | 50 to 175 g |
| 70 kg | 154.3 lb | 56 g | 50 to 175 g |
| 80 kg | 176.4 lb | 64 g | 50 to 175 g |
| 90 kg | 198.4 lb | 72 g | 50 to 175 g |
| 100 kg | 220.5 lb | 80 g | 50 to 175 g |
Check 50 kg. 0.8 × 50 = 40 g. The AMDR floor is 50 g. At 2,000 kcal, a 50 kg adult’s RDA sits 10 g under the 10 percent line. The card will show both. The RDA did not shrink because the calories are high. The RDA never reads the calories.
Check 63 kg. 0.8 × 63 = 50.4, and the card rounds that to 50 g. The AMDR floor is also 50 g. They meet on the display. The unrounded RDA is 0.4 g higher.
From 70 kg to 80 kg the RDA moves from 56 g to 64 g. That 8 g is 10 × 0.8, with no rounding in the way.
Fig 3 · 1/3
RDA grams at the same 2,000 kcal
Each kilogram adds 0.8 g. The card rounds to a gram.
Adult RDA
50 kg
40 g
70 kg
56 g
100 kg
80 g
50 kg is 40 g. 70 kg is 56 g.
100 kg is 80 g. The 90 kg row in the table is 72 g.
Fig 4 · 1/6
RDA as weight rises
Calories stay at 2,000. The line is 0.8 g per kilogram, then rounded.
RDA grams
- RDA
| Point | RDA |
|---|---|
| 45 kg | 36 |
| 57 kg | 46 |
| 70 kg | 56 |
| 80 kg | 64 |
| 95 kg | 76 |
| 110 kg | 88 |
45 kg is 36 g. 70 kg is 56 g.
95 kg is 76 g. 110 kg is 88 g.
The 57 kg point is Example 3’s 46 g. The 95 kg point is 0.8 × 95 = 76 g, and 95 kg displays as 209.4 lb. The line steps by 0.8 g per kilogram, then the label rounds. From 45 kg to 57 kg the raw gain is 9.6 g and the displayed gain is 46 − 36 = 10 g.
Example 6: what if I change only the calories
Weight stays 70 kg. The RDA stays 56 g on every row. The card still shows 154.3 lb.
| Calories | AMDR low | AMDR high | Where 56 g sits |
|---|---|---|---|
| 1,200 | 30 g | 105 g | 26 g above the floor |
| 1,500 | 38 g | 131 g | 18 g above the floor |
| 1,800 | 45 g | 158 g | 11 g above the floor |
| 2,000 | 50 g | 175 g | 6 g above the floor |
| 2,240 | 56 g | 196 g | on the floor |
| 2,400 | 60 g | 210 g | 4 g under the floor |
| 2,842 | 71 g | 249 g | 15 g under the floor |
| 3,000 | 75 g | 263 g | 19 g under the floor |
| 3,500 | 88 g | 306 g | 32 g under the floor |
The floor meets the RDA when calories × 0.10 ÷ 4 = 56. That is 224 kcal of protein, which is 2,240 kcal for the day. 2,240 × 0.10 ÷ 4 = 56 exactly, and the high end is 2,240 × 0.35 ÷ 4 = 196 g.
Above 2,240 kcal, the 10 percent line is a bigger gram number than the RDA. The calculator still prints the RDA as the headline. It does not replace it with the floor.
Two rows are worth doing by hand because the rounding is easy to miss.
1,500 × 0.10 ÷ 4 = 37.5, displayed as 38 g. 1,500 × 0.35 ÷ 4 = 131.25, displayed as 131 g.
3,500 × 0.10 ÷ 4 = 87.5, displayed as 88 g. 3,500 × 0.35 ÷ 4 = 306.25, displayed as 306 g.
The 2,842 kcal row is the default day from the calorie post: male equation, 70 kg, 175 cm, age 35, PAL 1.75, displayed as 2,842 kcal. Paste that into this calculator and the RDA is still 56 g. The band becomes 71 g to 249 g. 2,842 × 0.10 ÷ 4 = 71.05, displayed as 71 g.
The same post’s female equation on that body is 2,551 kcal. 2,551 × 0.10 ÷ 4 = 63.775, displayed as 64 g, still with an RDA of 56 g. Its age-28 example is 62 kg and 2,093 kcal. 0.8 × 62 = 49.6, displayed as 50 g, and the floor is 2,093 × 0.10 ÷ 4 = 52.325, displayed as 52 g. The floor is 2 g above the RDA on that card. Its larger example is 85 kg and 3,525 kcal. 0.8 × 85 = 68 g, and the floor displays as 88 g.
Fig 5 · 1/2
RDA against the 10 percent line
Weight stays 70 kg, so the RDA stays 56 g.
grams
- RDA
- AMDR low
| Category | RDA | AMDR low |
|---|---|---|
| 1,500 kcal | 56 | 38 |
| 2,000 kcal | 56 | 50 |
| 2,400 kcal | 56 | 60 |
| 3,500 kcal | 56 | 88 |
At 1,500 kcal the floor is 38 g. At 2,000 kcal it is 50 g.
At 2,400 kcal the floor is 60 g. At 3,500 kcal it is 88 g.
Example 7: typing pounds into the kilogram field
The field wants kilograms. A common slip is to type the pound figure you already know.
Example 1’s 70 kg displays as 154.3 lb. Type 154 into the kilogram field, with calories still at 2,000.
RDA: 0.8 × 154 = 123.2, displayed as 123 g
AMDR: still 50 g to 175 g, because the calories did not change
Weight on the card: 154 × 2.204622622 = 339.512, displayed as 339.5 lb
The card is doing the formula you asked for. 154 kg is a much heavier body than 70 kg. The RDA jumped from 56 g to 123 g, a displayed gap of 67 g. The unrounded gap is 123.2 − 56 = 67.2 g.
Divide the pounds by 2.204622622 before you type them, or type the kilograms you actually have. 154.3 ÷ 2.204622622 comes back to 70 kg, and the RDA comes back to 56 g.
The AMDR did not catch this. It only reads calories. A pound typed as a kilogram leaves the band alone and inflates the headline.
Example 8: calories at zero, and the half-gram round
Set weight to 70 and calories to 0.
The result is 56 g. The details stop after the weight and the rate. There is no 50 g line and no 175 g line. The formula skips the AMDR when calories are not above 0. That is the right card when you do not have a calorie number yet. Get one from the calorie calculator, then come back.
The half-gram case is 57 kg in Example 3: 45.6 displays as 46. Another one is 63 kg at 2,000 kcal: 50.4 displays as 50, level with the AMDR floor. A value that lands on .5 rounds away from zero. 0.8 × 56.875 = 45.5, and that displays as 46 g. You will not hit 56.875 on a whole-kilogram entry. You will hit 57, and 45.6 takes the same path to 46.
The examples next to each other
| Case | Weight | Calories | RDA | AMDR low | AMDR high |
|---|---|---|---|---|---|
| 1. Default | 70 kg | 2,000 | 56 g | 50 g | 175 g |
| 2. Guide example | 80 kg | 2,400 | 64 g | 60 g | 210 g |
| 3. 57 kg reference | 57 kg | 1,800 | 46 g | 45 g | 158 g |
| 4. Smaller | 45 kg | 1,400 | 36 g | 35 g | 122 g |
| 4. Larger | 110 kg | 3,000 | 88 g | 75 g | 263 g |
| 5. Light, same calories | 50 kg | 2,000 | 40 g | 50 g | 175 g |
| 5. 63 kg, rounding | 63 kg | 2,000 | 50 g | 50 g | 175 g |
| 5. 100 kg | 100 kg | 2,000 | 80 g | 50 g | 175 g |
| 6. Low calories | 70 kg | 1,200 | 56 g | 30 g | 105 g |
| 6. Floor meets RDA | 70 kg | 2,240 | 56 g | 56 g | 196 g |
| 6. Calorie-post day | 70 kg | 2,842 | 56 g | 71 g | 249 g |
| 6. High calories | 70 kg | 3,500 | 56 g | 88 g | 306 g |
| 7. 154 typed as kg | 154 kg | 2,000 | 123 g | 50 g | 175 g |
| 8. Calories at 0 | 70 kg | 0 | 56 g | ||
| 8. Calorie post, 62 kg | 62 kg | 2,093 | 50 g | 52 g | 183 g |
| 8. Calorie post, 85 kg | 85 kg | 3,525 | 68 g | 88 g | 308 g |
Open the protein calculator and type kilograms, then a calorie total if you want the band. The calorie calculator can supply that total. The BMI calculator will take the same kilograms and a height, and it will not change this RDA. Ask a clinician before you treat 0.8 g per kg as a target for pregnancy, illness, or heavy training.