Understanding and Calculating Nutrient PPM

Trout2012

Trout2012

Well-Known Member
Renfro said:
Understanding and Calculating Nutrient PPM

PPM (Parts Per Million) can seem like a mystery but it’s actually very simple. Basically the idea is to quantify how much “stuff” is in your water.

PPM is commonly measured by a grower using an electronic pen which measures the electrical conductivity of the water (EC). This is then converted to a PPM number with a conversion factor. Since different substances in the water will conduct electricity with varying degrees of resistance we must understand this number is only an estimate.

This is all fine and dandy for figuring out how much of everything is in your mix but what if you want to get more specific and determine how much of a given nutrient is present in your mix.
If we want to calculate how much of a given nutrient is in the mix using the label ingredient percentages we can make that happen with a little math.

Dry Salts - Mass Measurements

Say we are adding half a gram of Calcium Nitrate to 1 Liter of H2O and we want to see how much calcium and nitrogen we added in PPM, we know the calcium nitrate is 19% Calcium.

500mg x 0.19 = 95 mg/L (ppm) Calcium
500mg x 0.155 = 77.5 mg/L (ppm) Nitrogen

To do the math for 1 gram per gallon,

First get the mg per liter from gram per gallon:

1000mg / 3.785 = 264.2007926023778

Grams per Gallon x 264.2007926023778 x Label Percentage = PPM

Calcium Nitrate is 15.5% Nitrogen therefore we get,

1 gram x 264.2 x 0.155 = 40.95 PPM

of nitrogen by adding 1 gram to a gallon.

So for basic dry (mass) calcs just take 264 times the percentage and you know how many PPM of something you get with a gram per gallon.

The calcium nitrate also has 19% calcium.

1 gram x 264.2 x 0.19 = 50.19 PPM

of calcium by adding 1 gram to a gallon.

To figure out how much of something to add to get a given PPM you divide the target PPM by the percentage

So lets say you want 40 PPM of Magnesium from Epsom salt. Epsom is 9.7% Magnesium and 13% Sulfur.

40 / 0.097 = 412mg/L

and

412 x 3.785 = 1560.8mg or 1.56 grams per gallon to get 40 PPM of Magnesium.

Now that also brings some sulfur and we can calculate that,

412mg/L times 0.13 = 53.56 PPM

of Sulfur comes along with the 40 PPM of magnesium.

Phosphorous and Potassium - Beasts of another nature

It should be noted that P & K are different animals depending on how they are put in the mix.

By convention in the U.S. the fertilizer label lists the percentage P2O5 instead of the percent P. Similarly, the labels lists the percentage K2O instead of the percent K. This means we have to take into account conversion factors to calculate the percent elemental P and K.

To convert P2O5 to P multiply by 0.4364
To convert P to P2O5 multiply by 2.2915
To convert K2O to K multiply by 0.8301
To convert K to K2O multiply by 1.2047

Liquid Nutrients and Specific Gravity - Volume Measurements

It gets more complicated when mixing by volume and not mass, liquid nutrients. In this case you must take density into account.

Since the specific gravity of a nutrient isn't commonly listed on the label we must weigh a volume of the nutrient and calculate it's specific gravity.

For example, I just put 100mL of GH Micro in a graduated cylinder and it weighed about 121.2 grams. So if I do some math on the GH micro, 1mL per gallon, the label says it has 5% calcium.

1 mL per gallon x 264.2 x .05 = 13.2 PPM of calcium

BUT when we take into account the extra mass in the mL we multiply that by a specific gravity of 1.212 (according to my most likely not accurate measurement) and then we get 16 PPM of calcium by adding 1 mL of Micro to a gallon of water.

1 mL per gallon x 264.2 x .05 x 1.212 = 16 PPM of calcium

I hope this helps explain PPM and I regret any errors in my math. Please contribute if you see anything important I missed or any unfortunate errors in my work. I didn't go into conversions of PPM from EC as thats really another subject and very simple. - Renfro
Click to expand...
Renfro said:
Understanding and Calculating Nutrient PPM

PPM (Parts Per Million) can seem like a mystery but it’s actually very simple. Basically the idea is to quantify how much “stuff” is in your water.

PPM is commonly measured by a grower using an electronic pen which measures the electrical conductivity of the water (EC). This is then converted to a PPM number with a conversion factor. Since different substances in the water will conduct electricity with varying degrees of resistance we must understand this number is only an estimate.

This is all fine and dandy for figuring out how much of everything is in your mix but what if you want to get more specific and determine how much of a given nutrient is present in your mix.
If we want to calculate how much of a given nutrient is in the mix using the label ingredient percentages we can make that happen with a little math.

Dry Salts - Mass Measurements

Say we are adding half a gram of Calcium Nitrate to 1 Liter of H2O and we want to see how much calcium and nitrogen we added in PPM, we know the calcium nitrate is 19% Calcium.

500mg x 0.19 = 95 mg/L (ppm) Calcium
500mg x 0.155 = 77.5 mg/L (ppm) Nitrogen

To do the math for 1 gram per gallon,

First get the mg per liter from gram per gallon:

1000mg / 3.785 = 264.2007926023778

Grams per Gallon x 264.2007926023778 x Label Percentage = PPM

Calcium Nitrate is 15.5% Nitrogen therefore we get,

1 gram x 264.2 x 0.155 = 40.95 PPM

of nitrogen by adding 1 gram to a gallon.

So for basic dry (mass) calcs just take 264 times the percentage and you know how many PPM of something you get with a gram per gallon.

The calcium nitrate also has 19% calcium.

1 gram x 264.2 x 0.19 = 50.19 PPM

of calcium by adding 1 gram to a gallon.

To figure out how much of something to add to get a given PPM you divide the target PPM by the percentage

So lets say you want 40 PPM of Magnesium from Epsom salt. Epsom is 9.7% Magnesium and 13% Sulfur.

40 / 0.097 = 412mg/L

and

412 x 3.785 = 1560.8mg or 1.56 grams per gallon to get 40 PPM of Magnesium.

Now that also brings some sulfur and we can calculate that,

412mg/L times 0.13 = 53.56 PPM

of Sulfur comes along with the 40 PPM of magnesium.

Phosphorous and Potassium - Beasts of another nature

It should be noted that P & K are different animals depending on how they are put in the mix.

By convention in the U.S. the fertilizer label lists the percentage P2O5 instead of the percent P. Similarly, the labels lists the percentage K2O instead of the percent K. This means we have to take into account conversion factors to calculate the percent elemental P and K.

To convert P2O5 to P multiply by 0.4364
To convert P to P2O5 multiply by 2.2915
To convert K2O to K multiply by 0.8301
To convert K to K2O multiply by 1.2047

Liquid Nutrients and Specific Gravity - Volume Measurements

It gets more complicated when mixing by volume and not mass, liquid nutrients. In this case you must take density into account.

Since the specific gravity of a nutrient isn't commonly listed on the label we must weigh a volume of the nutrient and calculate it's specific gravity.

For example, I just put 100mL of GH Micro in a graduated cylinder and it weighed about 121.2 grams. So if I do some math on the GH micro, 1mL per gallon, the label says it has 5% calcium.

1 mL per gallon x 264.2 x .05 = 13.2 PPM of calcium

BUT when we take into account the extra mass in the mL we multiply that by a specific gravity of 1.212 (according to my most likely not accurate measurement) and then we get 16 PPM of calcium by adding 1 mL of Micro to a gallon of water.

1 mL per gallon x 264.2 x .05 x 1.212 = 16 PPM of calcium

I hope this helps explain PPM and I regret any errors in my math. Please contribute if you see anything important I missed or any unfortunate errors in my work. I didn't go into conversions of PPM from EC as thats really another subject and very simple. - Renfro
Click to expand...
Is there a way to tell exactly what elements are in say well water before the addition of the nutes? They say our water contains a high amount of calcium here! Awesome info here!!!
 
Renfro

Renfro

Well-Known Member
Trout2012 said:
Ok thanks I'm just getting into the ppm stuff just bought a meter tested my water today. Out of faucet was 132 is that fairly normal?
Click to expand...
It's pretty normal yeah. Mine is usually in the mid 150's but it tends to go up into the 200's for a few months in the winter. So it can vary depending on your municipal water source. It's nice to have your water analyzed to see whats in it. We have the normal calcium but sometimes out magnesium spikes and you notice yellow staining around the sink drains. Sometimes it's iron and you get the rust colored stains. It's good to know whats in the water so you don't add to much or not enough. If your water already has enough calcium and magnesium then no need for calmag or epsom salt. You may have plenty of calcium and just need epsom salt.
 
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Trout2012

Trout2012

Well-Known Member
Thanks you have been a tremendous help!! I didn't understand all of this stuff. I'll have to get my water checked out, I know my neighbor had a fountain it clogged up with white stuff in just a few months. The water tastes and smells good, but now I want to know what's in it!!
 
Trout2012

Trout2012

Well-Known Member
I know their well is the old point style and shallow. I had a new well put in about 11 years ago, it 79 feet deep. My other well just quit flowing slowy. Probably clogged with what ever it is!!
 
Renfro

Renfro

Well-Known Member
Trout2012 said:
I know their well is the old point style and shallow. I had a new well put in about 11 years ago, it 79 feet deep. My other well just quit flowing slowy. Probably clogged with what ever it is!!
Click to expand...
Hmm, sounds like sediment. I would have a sediment filter installed on the homes water supply for sure.
 
Renfro

Renfro

Well-Known Member
I added more products and made adding products a little easier. I am looking for requests on any nutrient products people want added to the calculator. With products that I don't have a specific gravity on I am entering them by mass and setting it so user inputting a specific gravity will modify the PPM's so you can now use mL volume measurements with that product.

So dry or wet, what products do you all want added? lol
 
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