She Blinded Me with....Math. Help!

cortesd
cortesd Posts: 58 Member
edited November 2024 in Food and Nutrition
I'll admit that math has never been my strong point. I am embarrassed that I can't figure this out on my own, but not too proud to ask for help.

So, dinner tonight included 411g of raw sweet potatoes (calories from USDA website = 353 kcal) , sliced, and baked without any added oil (just a scosh of salt). The weight of the finished product is 131g. So if I ate a 50g portion, how many calories did I eat? :s

Thanks!!!
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Replies

  • usmcmp
    usmcmp Posts: 21,219 Member
    edited November 2015
    You go to your food diary and click add, then search for "Sweet potato, cooked, baked in skin, flesh, with salt" and under the how much part you put in .5 then click the arrow and select 100g.

    You ate 50 grams of baked sweet potato. It doesn't matter how much you started with or how much you ended up with, only how much you ate.
  • NeonStrikeVi
    NeonStrikeVi Posts: 61 Member
    (50/411)*353 = 43kcal (rounded up).
  • carinaut
    carinaut Posts: 15 Member
    I'd say the 131 g of finished product contain the same amount of calories as the 411 g of raw potatoes. The calories stay the same, only the percentage of water decreases. So my calculation would be the following: (353*50)/131=135 kcal rounded up. But I must say, I am surprised they changed their weight that significantly. Did you peel them after weighing and before baking? Well, but I suppose if you cut them into thin slices and make them really crunchy, the weight can go from 411 g to 131 g.
  • cortesd
    cortesd Posts: 58 Member
    carinaut wrote: »
    I'd say the 131 g of finished product contain the same amount of calories as the 411 g of raw potatoes. The calories stay the same, only the percentage of water decreases. So my calculation would be the following: (353*50)/131=135 kcal rounded up. But I must say, I am surprised they changed their weight that significantly. Did you peel them after weighing and before baking? Well, but I suppose if you cut them into thin slices and make them really crunchy, the weight can go from 411 g to 131 g.

    Yep. Made homemade chips. I was surprised that they lost that much weight too. Hmmm...guess that would be "water weight," huh? :D
  • cortesd
    cortesd Posts: 58 Member
    usmcmp wrote: »
    You go to your food diary and click add, then search for "Sweet potato, cooked, baked in skin, flesh, with salt" and under the how much part you put in .5 then click the arrow and select 100g.

    You ate 50 grams of baked sweet potato. It doesn't matter how much you started with or how much you ended up with, only how much you ate.

    Thanks usmcmp. *face palm* Maybe I should wait until AFTER I eat to log stuff since my brain is always fuzzy beforehand. ;)
  • HeidiCooksSupper
    HeidiCooksSupper Posts: 3,831 Member
    edited November 2015
    You started with a total amount of sweet potatoes equivalent to 353 calories. You consumed 50/131 of the final product. What is 50/131 of 353? Take your calculator and multiply 353 by 50. Divide that total by 131. You ate 135 calories.
  • cortesd
    cortesd Posts: 58 Member
    Hmm, getting more confused since the posted suggestions on calculations differ by almost 100 cals. Maybe I'll just stick to raw foods...
  • stealthq
    stealthq Posts: 4,298 Member
    edited November 2015
    HeidiCooksSupper wrote: »
    You started with a total amount of sweet potatoes equivalent to 353 calories. You consumed 50/131 of the final product. What is 50/131 of 353? Take your calculator and multiply 353 by 50. Divide that total by 131. You ate 135 calories.

    The calculations that look like this ^^^ are correct.

    The earlier poster got confused and calculated based on eating 50g of the uncooked sweet potato (50/411).
  • Abby2205
    Abby2205 Posts: 253 Member
    NeonStrikeVi wrote: »
    (50/411)*353 = 43kcal (rounded up).

    This is wrong. OP ate 50 g of cooked sweet potato. The calculation is (50/131) x 353 = 135 calories.
  • Kalikel
    Kalikel Posts: 9,603 Member
    edited November 2015
    If I read it right, you said there were 353 calories in 411g. If that's the case and you ate 51g, it's about 44 calories.

    411g = 353 calories

    411/411 g = 353/411 calories

    1 g = .8588 calories

    .8588 calories x 51 (number of grams) = 43.79

    ~ 44 calories
  • ahoy_m8
    ahoy_m8 Posts: 3,053 Member
    Kalikel wrote: »
    If I read it right, you said there were 353 calories in 411g. If that's the case and you ate 51g, it's about 44 calories.

    411g = 353 calories

    411/411 g = 353/411 calories

    1 g = .8588 calories

    .8588 calories x 51 = 43.79

    ~ 44 calories

    Raw vs cooked. OP ate 50g cooked. 411g raw = 131g cooked. Hence OP ate 50/131 of the potato.
  • blankiefinder
    blankiefinder Posts: 3,599 Member
    edited November 2015
    Ay yi yi.... it is 50/131g and the equation is as posted above, (353*50)/131=135 kcal rounded up (total calories based on raw ingredient(s) times actual serving size divided by final product cooked weight). While usmcmp's method works great for this item, for other dishes its good to know that when figuring out calories of a finished product, you must compare it to the finished weight.

    So when you build a recipe in the recipe builder, you add the individual ingredients, weighed raw, and then weigh the final product, and calculate your number of servings from the final cooked product weight.
  • EvgeniZyntx
    EvgeniZyntx Posts: 24,208 Member
    edited November 2015
    So, in summary, two methods:

    USDA cooked data: There are 90 calories in 100 g of baked sweet potatoes. If you ate 50 g that is 45 calories.
    USDA raw data: 353*50/131 gives us 135 calories.

    That's quite the difference.
    My first guess is that there is an error in the USDA data everyone is referencing. Or weighing errors.








  • stevencloser
    stevencloser Posts: 8,911 Member
    50 grams out of 131 is 50/131 as a fraction of the whole. Times the starting weight of 411, you ate an equivalent of 157 grams raw potato.
    It's weird how it lost so much water during baking, didn't you pack it in aluminum foil?
  • belimawr
    belimawr Posts: 1,155 Member
    edited November 2015
    EvgeniZyntx wrote: »
    So, in summary, two methods:

    USDA cooked data: There are 90 calories in 100 g of baked sweet potatoes. If you ate 50 g that is 45 calories.
    USDA raw data: 353*50/131 gives us 135 calories.

    That's quite the difference.
    My first guess is that there is an error in the USDA data everyone is referencing. Or weighing errors.

    Quite a difference because 50g raw is not the same as 50g cooked, yet it is being used in both equations as the same quantity.

    Either use 50g when using the cooked calorie value, or adjust it to compare to the raw value (50g cooked in this case = ~157g raw).

    So, raw (157/411)*353 = ~135cal.

    (edited to correct typos)
  • EvgeniZyntx
    EvgeniZyntx Posts: 24,208 Member
    belimawr wrote: »
    EvgeniZyntx wrote: »
    So, in summary, two methods:

    USDA cooked data: There are 90 calories in 100 g of baked sweet potatoes. If you ate 50 g that is 45 calories.
    USDA raw data: 353*50/131 gives us 135 calories.

    That's quite the difference.
    My first guess is that there is an error in the USDA data everyone is referencing. Or weighing errors.

    Quite a difference because 50g raw is not the same as 50g cooked, yet it is being used in both equations as the same quantity.

    Either use 50g when using the cooked calorie value, or adjust it to compare to the raw value (50g cooked in this case = ~157g raw).

    So, raw (157/411)*353 = ~135cal.

    (edited to correct typos)

    I used the cooked data for the cooked calc.
    So, again. Quite the difference.

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  • belimawr
    belimawr Posts: 1,155 Member
    edited November 2015
    @EvgeniZyntx the problem with the math here is not the weighing itself, but that the OP baked them to the point as to make them chips. With the amount of water lost, it can no longer be compared to your normal baked potato using the baked potato data, and therefore the raw values must be used.
  • Clarewho
    Clarewho Posts: 494 Member
    I always try and use the raw values for this reason, a raw sweet potato is equal to all other raw sweet potatoes yes? So just weigh the raw potato and log that. Then if you add anything in the cooking process (eg oil), log that as well. Don't bother trying to weigh cooked food.
  • pondee629
    pondee629 Posts: 2,469 Member
    cortesd wrote: »
    I'll admit that math has never been my strong point. I am embarrassed that I can't figure this out on my own, but not too proud to ask for help.

    So, dinner tonight included 411g of raw sweet potatoes (calories from USDA website = 353 kcal) , sliced, and baked without any added oil (just a scosh of salt). The weight of the finished product is 131g. So if I ate a 50g portion, how many calories did I eat? :s

    Thanks!!!

    411g raw = 131g cooked = 353 cals. These are our givens. you ate 50g cooked. Therefore:
    50g (amt eaten cooked)/ 131g (amt when cooked) * 353kcal (total cal when cooked)= 134.73 (135 kcals) cal eaten.
  • cortesd
    cortesd Posts: 58 Member
    411g raw = 131g cooked = 353 cals. These are our givens. you ate 50g cooked. Therefore:
    50g (amt eaten cooked)/ 131g (amt when cooked) * 353kcal (total cal when cooked)= 134.73 (135 kcals) cal eaten.

    Okay, I think this makes sense. But how do I log it? I've now got to figure out what % of the raw I ate so I can accurately log the amount in MPF. I also fear that all my previous entries for the last few months have been waaay off. To me, 100 cals is a lot to be off by for one item!

  • JohnBarth
    JohnBarth Posts: 672 Member
    You ate 38% of the total calories. That means you ate 38% of 411 raw grams or 157 raw grams. Find the "sweet potato, raw" entry, choose the 100g portion and enter your servings as 1.57
  • EvgeniZyntx
    EvgeniZyntx Posts: 24,208 Member
    edited November 2015
    belimawr wrote: »
    @EvgeniZyntx the problem with the math here is not the weighing itself, but that the OP baked them to the point as to make them chips. With the amount of water lost, it can no longer be compared to your normal baked potato using the baked potato data, and therefore the raw values must be used.

    ah, chips, missed that.
  • NeonStrikeVi
    NeonStrikeVi Posts: 61 Member
    Abby2205 wrote: »
    NeonStrikeVi wrote: »
    (50/411)*353 = 43kcal (rounded up).

    This is wrong. OP ate 50 g of cooked sweet potato. The calculation is (50/131) x 353 = 135 calories.

    Thought OP used 50g of the raw sweet potato :neutral: .

  • Derf_Smeggle
    Derf_Smeggle Posts: 610 Member
    edited November 2015
    So, a couple of things. First, the USDA "cooked, baked, with skin" value is derived from a very specific prep method, cooking temperature, and cooking time.

    Baking sweet potato chips is not equal to their values because you will have changed the method, time, and temp.

    Second, I think it is slightly simpler to figure out your batch multiplier. A batch multiplier allows you to convert the cooked value back to the equal amount of raw product. You can then log the raw product. I'll show my work, but I boldfaced the important part.

    Started out with:
    411g raw = 353kCal

    Ended with:
    131g cooked = 353kCal

    Which means:
    411g raw = 131g cooked (both equal 353kCal)

    411 raw / 131 cooked = 3.14 multiplier

    So multiply your cooked product by the multiplier:
    50g cooked x 3.14 = 157g raw

    You log 157g of raw product (which is equal to 134.8kCal).







  • pondee629
    pondee629 Posts: 2,469 Member
    "3.14 multiplier" Pi?

  • blankiefinder
    blankiefinder Posts: 3,599 Member
    Just going to say, I would use the recipe builder for this, sole ingredient the raw sweet potato, number of servings the number of grams in cooked product, then serving size is number of grams consumed. Easy peasy, no math involved, and can edit recipe with the weight of the raw the next time you make it
  • EvgeniZyntx
    EvgeniZyntx Posts: 24,208 Member
    pondee629 wrote: »
    "3.14 multiplier" Pi?

    I like pie.
  • Derf_Smeggle
    Derf_Smeggle Posts: 610 Member
    edited November 2015
    pondee629 wrote: »
    "3.14 multiplier" Pi?
    I saw that too. Almost cracked a joke, but didn't want to confuse the issue. :)

    blankiefinder wrote: »
    Just going to say, I would use the recipe builder for this, sole ingredient the raw sweet potato, number of servings the number of grams in cooked product, then serving size is number of grams consumed. Easy peasy, no math involved, and can edit recipe with the weight of the raw the next time you make it
    I use the recipe builder a lot and do it that way. However, it seems silly when you just have one item and can simply divide raw weight by cooked weight to get a multiplier. That multiplier simply converts cooked weight back to raw portions.
  • belimawr
    belimawr Posts: 1,155 Member
    edited November 2015
    Clarewho wrote: »
    I always try and use the raw values for this reason, a raw sweet potato is equal to all other raw sweet potatoes yes? So just weigh the raw potato and log that. Then if you add anything in the cooking process (eg oil), log that as well. Don't bother trying to weigh cooked food.

    Exactly how I do it. Too many variables once cooked that are going to mess you up.
    pondee629 wrote: »
    "3.14 multiplier" Pi?

    mmm... pi... *drools*
  • Derf_Smeggle
    Derf_Smeggle Posts: 610 Member
    belimawr wrote: »
    Clarewho wrote: »
    I always try and use the raw values for this reason, a raw sweet potato is equal to all other raw sweet potatoes yes? So just weigh the raw potato and log that. Then if you add anything in the cooking process (eg oil), log that as well. Don't bother trying to weigh cooked food.

    Exactly how I do it. Too many variables once cooked that are going to mess you up.
    At issue is that the OP didn't eat the whole batch of sweet potatoes they prepared....

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