Whether you're looking to make your blends be more consistent, avoid clean up, avoid cross contamination, mix larger batch sizes, or are just trying to avoid the long term cost of buying syringes and other mixing instruments, well, this is written for you. Supplies There are very few supplies that are REQUIRED to mix by weight. They are: 1.) Scale - Scales come in many different varieties and there are tons that would work for most people. There is one major thing you need to AVOID when looking for a scale. You need a scale that DOES NOT have an AUTO-SHUT OFF feature, or at least if it has one, it needs to be on a long delay. A lot of scales by default have a 10 or 15 second auto-shut off, this can mess you up very badly if your scale shuts off while you are trying to add ingredients to a mix. I recommend: American Weigh Scales LB-501 Digital Kitchen Scale 2.) Pipettes - These are only needed if you have flavoring bottles that do NOT have dropper tops. You can find them on Amazon for ~$20 for a box of 500. This will last the average DiY'er a very very very long time. 3.) Bottles - You will want some dropper bottles for adding PG/VG and Nicotine to your mixes. I'd recommend at least an 8oz bottle, however, if you mix smaller quantities for the most part, you can probably survive with 4oz bottles for PG and VG and a 1 oz for 100mg NIC. I use 4oz for nic and 8oz for PG/VG. You can find these on amazon for under $3 each, or go to a company like www.usplastic.com and get them much cheaper (but have to pay higher shipping). Calculator Not too much I need to say here other than give you some basic values. There's only one Calculator that I have used since I started DiY'ing and it works wonderfully for mixing by weight. Calculator Link. The basic values that you need to know for mixing by weight are below. Weight of PG: 1.038 grams per ml Weight of VG: 1.26 grams per ml Weight of Pure Nicotine: 1.01 grams per ml Weight of 100mg in PG: 1.0352 grams per ml Weight of 100mg in VG: 1.235 grams per ml If you have a mix of Nicotine that is not 100mg the calculation is fairly simple: 48mg VG based nicotine solution. That's 4.8% nicotine in VG. Let's just pretend we have 100ml as it's easier than dealing with a lot of decimal points. The total weight of nicotine in this solution would be 1.01 x 4.8 = 4.848g. Add in the other 95.2ml of VG and you have 1.26 x 95.2 = 119.952g. Add the two together, and you get 124.8 grams in 100ml solution or 1.248 grams per ml. The same can be done for any nicotine base or solution if it isn't shipped to you with an MSDS or you no longer have it. When it comes to flavors, there are a couple of thoughts/theories surrounding mixing by weight when dealing with flavors. Many people enter the specific gravity as indicated on an MSDS for every flavor that they have. I feel this is a complete waste of time. After searching hundreds of MSDS sheets for flavors, all flavors fall into a range of .93g per ml to 1.07g per ml. In order to achieve personal consistency for your juices though, all that is relevant is that you use the SAME value, every time for any given flavor. I simply use a value of 1. This means that whether or not my flavors actually weigh 1 gram per ml, I always pretend they do. Percentages in any given recipe of mine will always be the exact same for me, however, if I am trying to recreate someone elses recipe, or they are mixing mine, there's a chance I'll be off a little bit (no more than 7% which is about the margin of error most people get when mixing by volume). Method The method is pretty subjective but I'll share what I do. It's fairly simple. Any scale you buy should come with a 'tare' button. This resets the scale to zero regardless of the weight on it. This is a button you use quite frequently. Basically, start off by setting your bottle on the scale, whatever it is you want to mix into. Sometimes for me this is finished bottles, other times when I'm making larger batches, it's 250ml Amber glass bottles. Now your bottle is on the scale, turn your scale on, this starts your scale @ 0.00g. If you turned it on first and set your bottle on after, no big deal, just press the 'tare' button. Now, The calculator I linked above, gives you the weights you need to add for your Nicotine, VG, PG, and each flavor. I always go in order so I don't miss anything or forget my place (I also have my bottles set up in the same orderly line in my mixing space just to make sure). For example: I'm making a 15ml batch of my Princess Cake (fruitier version recipe). I'm using 100mg VG nicotine, and am looking for an end result of 40/60 PG/VG. The calculator gives me these outputs. I start by adding 0.556 grams of nicotine to my bottle, I round this to 0.56 as your scale likely only reads to the hundredth (at least mine does, thousandth readings on a scale will cost you ~20x the price of the scale). Then press 'tare'. Next I add my PG (4.476g) rounded to 4.48g. Then press 'tare'. Then VG 10.773 grams rounded to 10.77. Then press 'tare'. Then add your flavors pressing tare after each one. Before you know it, you've mixed your first bottle and have no mess to clean up. Congratulations, you just mixed your first batch of juice by weight. Any questions, shoot away.