Calculate the PG and VG volumes, weights, and final ratio for any base mix, from a target PG/VG ratio, from two liquids blended together, or from what is already in the bottle.
PG VG Ratio Formula
The PG/VG ratio is a volume percentage split of a two component base: propylene glycol (PG) and vegetable glycerin (VG). Every mode uses PG volume divided by PG plus VG volume. Neutral flavor volume is excluded from that ratio and is reported separately as a share of the whole batch.
Component volumes from a target ratio
- V_PG = PG-accounted volume before subtracting PG-carried flavor (mL)
- V_VG = VG-accounted volume before subtracting VG-carried flavor (mL)
- V_T = PG plus VG volume, excluding neutral flavor (mL)
- P = target PG percentage of the PG plus VG portion (%)
Ratio from volumes you already have
- P = PG percentage of the mix (%)
- V_PG, V_VG = measured volumes of each component (mL)
Final ratio after blending two liquids
- P_F = PG percentage of the finished blend (%)
- V_A, V_B = volumes of liquid A and liquid B (mL)
- P_A, P_B = PG percentages of liquid A and liquid B (%)
Correcting an existing mix to a target ratio
- V_VGadd = vegetable glycerin to add when the target PG is lower than the current PG (mL)
- V_PGadd = propylene glycol to add when the target PG is higher than the current PG (mL)
- V_C = current volume in the bottle (mL)
- V_PG = propylene glycol already in the bottle (mL)
- P_T = target PG percentage (%)
Batch weight from the volumes
- W = total weight of the base (g)
- 1.036 = density of propylene glycol at 20 C (g/mL)
- 1.261 = density of vegetable glycerin at 20 C (g/mL)
The four calculator modes map directly onto these expressions. Target mode treats the entire flavor volume as PG, VG, or neutral according to the selected assumption. It subtracts PG- or VG-counted flavor from that component’s amount to measure. With neutral flavor, the target applies to the remaining PG plus VG portion; whole-batch PG and VG percentages are lower. Volumes mode solves for P. Blend mode uses a volume weighted average of two PG/VG-only liquids. Correction mode adds one component without removing liquid; exact equality needs no addition, while 0% or 100% cannot be reached by a finite addition if the opposite component is present. Weights use approximate density presets, with flavor separately assumed to weigh 1.0 g/mL.
Common PG/VG Ratios, Weights, and Estimated Viscosity
PG and VG have different densities and viscosities, so equal component volumes do not have equal weights. The table below uses additive component volumes and approximate pure-component densities to estimate the weight and density of a 30 mL batch at 20 C. Viscosities are illustrative estimates from a log linear blending rule using 56 cP for PG and 1,412 cP for VG, not measured blend properties; purity, water content and temperature affect actual values.
| PG/VG | VG/PG | PG in 30 mL | VG in 30 mL | Mix density (g/mL) | Weight of 30 mL | Est. viscosity (cP) |
|---|---|---|---|---|---|---|
| 100/0 | 0/100 | 30.0 mL | 0.0 mL | 1.036 | 31.1 g | 56 |
| 60/40 | 40/60 | 18.0 mL | 12.0 mL | 1.126 | 33.8 g | 204 |
| 50/50 | 50/50 | 15.0 mL | 15.0 mL | 1.149 | 34.5 g | 281 |
| 40/60 | 60/40 | 12.0 mL | 18.0 mL | 1.171 | 35.1 g | 388 |
| 30/70 | 70/30 | 9.0 mL | 21.0 mL | 1.194 | 35.8 g | 536 |
| 20/80 | 80/20 | 6.0 mL | 24.0 mL | 1.216 | 36.5 g | 740 |
| 0/100 | 100/0 | 0.0 mL | 30.0 mL | 1.261 | 37.8 g | 1412 |
The second table shows how far the ratio moves when 10 mL of a second liquid is added to a 50 mL base. This is the arithmetic behind every complaint that a mix came out thinner than the label on the base bottle suggested.
| 50 mL base (PG/VG) | Final ratio with 10 mL of 100% PG | Final ratio with 10 mL of 50/50 | Final ratio with 10 mL of 100% VG |
|---|---|---|---|
| 20/80 | 33/67 | 25/75 | 17/83 |
| 30/70 | 42/58 | 33/67 | 25/75 |
| 40/60 | 50/50 | 42/58 | 33/67 |
| 50/50 | 58/42 | 50/50 | 42/58 |
Example Problems
Example 1: a 60 mL batch at 30% PG with flavoring
You want 60 mL of finished liquid at a 30/70 PG/VG ratio, and 10% of the bottle will be a PG based flavor concentrate.
- Flavor volume: 60 * 0.10 = 6 mL.
- Total PG the finished mix needs: 60 * 0.30 = 18 mL.
- The flavor is PG based, so it already supplies 6 mL of that. PG to measure: 18 – 6 = 12 mL.
- VG to measure: 60 * 0.70 = 42 mL.
- Check: 12 + 42 + 6 = 60 mL, and the PG share is (12 + 6) / 60 = 30%.
- By weight: 12 * 1.036 = 12.43 g PG and 42 * 1.261 = 52.96 g VG, plus 6 g of concentrate using the assumed 1.0 g/mL flavor density, for roughly 71.4 g total.
If you instead measured 18 mL of PG and 42 mL of VG, then added the 6 mL of PG-counted flavor, the additive total would be 66 mL with 24 mL counted as PG: 24 / 66 = about 36.36% PG, rather than 30%.
Example 2: correcting a mix that is too high in PG
You have 30 mL of base at 50% PG and you want it at 30% PG without discarding anything.
- PG already in the bottle: 30 * 0.50 = 15 mL.
- That 15 mL has to become 30% of the new total, so the new total is 15 / 0.30 = 50 mL.
- VG to add: 50 – 30 = 20 mL.
- Check: PG is 15 mL, VG is 15 + 20 = 35 mL, and 15 / 50 = 30% PG.
Note that the fix costs volume. You cannot lower the PG percentage without making more liquid, so plan the ratio before you mix if bottle size matters.
FAQ
Is a ratio like 70/30 written PG first or VG first?
Ratio order varies by label. Read the explicit PG/VG or VG/PG heading; the larger number alone does not identify either component. This calculator asks for PG percentage explicitly and reports both orders, so 30/70 PG/VG is the same composition as 70/30 VG/PG.
Why do the gram amounts not match the milliliter amounts?
PG has a density of about 1.036 g/mL and VG about 1.261 g/mL at 20 C, a difference of roughly 22%. A 50/50 mix by volume is therefore about 45.1% PG and 54.9% VG by weight. If you mix on a scale using the volume numbers as if they were grams, a nominal 50/50 comes out closer to 55/45 in favor of PG. Use appropriate density values when converting volume to grams; actual values depend on temperature, purity and water content, as well as measurement accuracy. The calculator prints both the volume and the weight for each component so you can pour or weigh from the same result.
Do the two volumes add up exactly?
The calculator treats component volumes as additive. Actual final volume can depend on composition, purity and temperature; no universal contraction percentage or correction is applied. If exact final volume matters, measure the finished mixture rather than assume the additive total. Separately, if any liquid you are blending contains nicotine, be aware that nicotine is acutely toxic by skin contact and ingestion. Handle and store it accordingly, and follow applicable local rules.
