How to Work Out a Cart’s Real Cost Per Dose

A cartridge price rarely tells the whole story. Two carts can cost the same while delivering very different amounts of active cannabinoids, and a lower-priced option may provide fewer usable doses after leakage, residue, or an inconsistent battery. Calculating the effective price per dose gives you a clearer way to compare products.

The calculation begins with the amount of THC or other cannabinoids in the cartridge, then considers how much you use for each session. For a simple estimate, divide the purchase price by the number of expected doses. A more realistic figure also allows for delivery charges, payment costs, unused oil, and the possibility that your actual puff size varies.

This matters for Australian consumers because cannabis access is shaped by local medical rules rather than a broad recreational retail market. Medicinal cannabis generally requires a prescription and supply through approved channels, while importing cartridges or buying products from overseas websites can create serious legal and safety issues. Prices should therefore be compared only between products you are legally permitted to obtain.

The same method works for THC carts, CBD cartridges, rosin pens, and other vape formats. It can also help compare a cartridge with flower, infused pre-rolls, or concentrates, although the label information and serving assumptions differ. The aim is a practical cost estimate, not a guarantee of effects or a substitute for medical advice.

Start With The Label And Total Product Weight

Find the cartridge’s net oil weight, usually shown in grams or milligrams. A 1 g cart contains approximately 1,000 mg of oil, while a 0.5 g cart contains approximately 500 mg. Oil weight is not the same as THC weight, because the oil may include cannabinoids, terpenes, and other ingredients.

Next, find the cannabinoid concentration. If a 1 g cartridge is labelled as 80% THC, multiply 1,000 mg by 0.80:

1,000 mg × 0.80 = 800 mg THC

That figure is the theoretical THC content. A cartridge labelled 70% THC would contain about 700 mg THC per gram, assuming the advertised net weight is accurate. For CBD, CBG, or a balanced formula, repeat the calculation for each cannabinoid rather than treating the entire oil volume as one active ingredient.

Product pages can use different conventions, so read whether the percentage applies to THC, total cannabinoids, or a specific extract. Information about the retailer and its range may be available through the store’s product background, but the package label and legally required documentation should remain the primary reference for any product you can lawfully access.

Convert The Price Into A Cost Per Milligram

The simplest comparison uses cost per milligram of the target cannabinoid. Divide the complete purchase price by the estimated cannabinoid content:

Effective cost per mg = total cost ÷ total mg of cannabinoid

For example, suppose a 1 g cartridge costs A$110 and contains 800 mg of THC. The calculation is:

A$110 ÷ 800 mg = A$0.1375 per mg

Rounded to the nearest cent, that is about 14 cents per milligram of THC. A 0.5 g cartridge costing A$75 and containing 350 mg THC would work out as:

A$75 ÷ 350 mg = A$0.214 per mg

The larger cartridge is cheaper by cannabinoid content, even though its upfront price is higher. This comparison is particularly useful when shopping within the Australian medicinal market, where product prices can vary substantially between pharmacies, formulations, and prescribed brands.

Estimate The Number Of Doses

A dose is not automatically the same as one puff. A short draw from one device may deliver much less vapour than a long draw from another, and voltage, airflow, oil thickness, and coil design all affect output. For a rough estimate, choose a conservative amount of THC per session based on your prescription instructions and previous experience.

If you estimate that one session uses 5 mg of THC, an 800 mg cartridge theoretically contains:

800 mg ÷ 5 mg = 160 sessions

At a purchase price of A$110, the theoretical cost is:

A$110 ÷ 160 sessions = A$0.69 per session

This number should not be treated as a recommended dose. New or inexperienced users should follow medical directions, begin only as instructed, and avoid increasing use simply because the arithmetic suggests that the product is inexpensive. A clinician or pharmacist can help interpret the prescribed amount and the formulation’s intended use.

Account For Real-World Waste

Theoretical calculations assume that every milligram reaches the user, which is unlikely. Oil can remain below the intake holes, cling to the cartridge walls, or become difficult to draw near the end. Some devices stop heating before all the oil is accessible. If you estimate 10% waste, multiply the labelled cannabinoid content by 0.90.

Using the earlier example:

800 mg × 0.90 = 720 mg usable THC

The adjusted cost becomes:

A$110 ÷ 720 mg = A$0.153 per usable mg

If each session uses 5 mg, the cart provides around 144 sessions rather than 160, making the adjusted cost approximately A$0.76 per session. A 10–20% waste allowance is only a planning estimate; a leaking, blocked, or defective product may perform much worse and should not be dismantled or modified.

Storage also affects value. In places such as Sydney, Brisbane, and Darwin, heat can thin oil, encourage leakage, or change how a cartridge behaves. Keeping a device upright, away from direct sun and hot cars, helps preserve usable contents. Follow the product’s storage instructions and do not use a cartridge that is cracked, contaminated, or visibly damaged.

Include The Costs Beyond The Sticker Price

The purchase price should include any delivery fee, dispensing charge, card surcharge, exchange-rate cost, or other unavoidable expense. For an Australian patient, a product’s apparent price may also be affected by pharmacy fees and the cost of a medical consultation or repeat prescription. Those costs are not always fairly assigned to one cartridge, so record them separately if you want to compare treatment expenses over a month.

For example, a cart priced at A$110 with A$12 delivery and a A$3 payment surcharge has a real transaction cost of A$125. With 720 mg of estimated usable THC, the adjusted price is:

A$125 ÷ 720 mg = A$0.174 per usable mg

That figure is more informative than the listed A$110. Bitcoin discounts, where offered by a retailer, should also be assessed against network fees, exchange-rate movement, and the legal status of the transaction. A discount does not make an unapproved import lawful, safer, or suitable for medical use.

When comparing products, keep the currency consistent. A Los Angeles price in US dollars cannot be compared directly with an Australian pharmacy price in Australian dollars. Convert it using the actual rate and add all costs before making a per-dose calculation. Products advertised online may also be unavailable for lawful delivery to Australia.

Compare Puff-Based And Milligram-Based Estimates

Some manufacturers publish an approximate number of puffs, such as 200 or 300 per cartridge. This can produce a second calculation:

Cost per puff = total cost ÷ stated puff count

A A$110 cartridge advertised as providing 250 puffs costs A$0.44 per puff. That number is useful for budgeting only if your draws resemble the manufacturer’s test conditions. A long draw may consume several times as much oil as a short draw, so “puff” is not a universal unit of dose.

A better personal estimate is to track the cartridge’s weight before and after a known number of sessions, if you have a suitable accurate scale and can do so safely. The difference in oil weight divided by the number of sessions gives approximate oil use per session. Multiply that amount by the labelled THC percentage to estimate cannabinoid use. Avoid opening or altering a cartridge, and do not rely on informal measurements where the device could leak or be damaged.

Puff counts are especially poor for comparing different hardware. A 0.5 g high-output cart may deliver stronger vapour per draw than a 1 g low-output device. For that reason, cost per labelled milligram, adjusted for waste, is usually the most consistent starting point, while cost per session provides a more personal budget estimate.

Apply The Calculation Safely In Australia

Australian cannabis law is different from the legal recreational systems operating in parts of the United States. Medicinal cannabis is generally accessed through a registered medical practitioner and supplied under the Therapeutic Goods Administration framework, with state and territory requirements also relevant. Recreational possession and supply remain unlawful, and importing cannabis vapes from overseas can breach customs and drug-importation rules.

Driving is another important local consideration. THC may affect driving ability, and roadside drug-testing programs operate in several jurisdictions, including New South Wales, Victoria, Queensland, and Western Australia. A prescription does not necessarily remove every driving restriction or guarantee that a roadside test will be disregarded. Check current guidance in your state and follow medical advice before driving, cycling in traffic, or operating machinery.

Keep a record of the product name, cannabinoid strength, cartridge size, purchase cost, and approximate number of sessions. A simple note can show whether the product is being used faster than expected and whether the prescribed amount is being followed. Never compensate for an expensive cart by taking larger draws or using it more often.

The most reliable calculation is therefore layered: determine the labelled cannabinoid content, subtract a realistic waste allowance, add unavoidable transaction costs, and divide by the number of medically appropriate sessions. That produces a practical estimate of the effective price per dose while keeping price comparisons separate from questions of legality, quality, and personal suitability.