Now, the devil is in the details. Here's where shop owners usually trip up.

1. Your base strength might not be what you think. Suppliers sometimes label nicotine base in percentages instead of mg/ml. 10% is 100mg/ml. 5% is 50mg/ml. Divide the percentage by 10 to get mg/ml. Always double-check this before you mix—a wrong assumption here ruins a whole batch.

2. PG/VG ratios affect the math slightly. Nicotine is usually suspended in a carrier like PG or VG. When you add nicotine base, you're also adding extra PG or VG, which dilutes your flavor ratio. If you're mixing from scratch, factor that in. For small batches, it's negligible; for large runs, it matters. The VG/PG Ratio Explained guide covers this in more detail.

3. Nicotine salts vs. freebase. The math is identical—both are measured in mg/ml. The difference is in how they feel at higher strengths. Salts are smoother, which is why they're common in disposables and pod systems. But don't let that confuse the calculation.

4. Always work in the same units. If you're thinking in percentages, convert everything to mg/ml first. Mixing units is the fastest way to make a 6mg/ml batch turn into 60mg/ml.