Small Jar, Real Maths: What Your CBD Really Costs Each Week
Photo: CBD face cream jar and serum bottles on bathroom shelf with calculator, via tb-static.uber.com
British bathrooms are not known for their spaciousness. A single shelf above the sink has to hold everything, so it's no wonder we shop with our eyes and buy the biggest tub we can afford. With CBD beauty, that instinct backfires. A fat jar of 250mg lotion can cost more per use than a slim 30ml serum, and a bottle that looks like better value often just contains more carrier oil.
So let's do the boring bit properly. Below is a way of comparing CBD products that ignores the marketing panel and uses three numbers instead.
The only three figures worth writing down
Milligrams per millilitre. This is concentration, and it's the number brands would rather you didn't calculate. Divide total CBD by bottle size. A 30ml serum with 300mg is 10mg per ml. A 100ml body lotion with 200mg is 2mg per ml. Same shelf, wildly different products.
Price per milligram. Take the price and divide by the total milligrams. £20 for 500mg is 4p per mg. £32 for 300mg is about 10.7p per mg. This tells you what you're paying for the CBD itself, before packaging, fragrance and the cost of the pretty box.
Price per use. The one that actually matters. Multiply the mg per ml by how much you dispense, then divide the price by the number of uses you'll get. A dropper typically delivers around 0.05ml per drop; a face-cream pump is usually somewhere between 0.3ml and 0.5ml. If a brand won't tell you, assume the stingier figure.
The sums, on the back of an old receipt
Here's a worked example. A 10ml bottle contains 500mg, so that's 50mg per ml — a strong oil. Two drops is roughly 0.1ml, or 5mg of CBD. The bottle gives you around 200 drops, so a two-drop evening dose lasts about 100 days. At £30 a bottle, that's 30p a day, or just over £2 a week.
That is where the £2 figure comes from. It is achievable — but only for one well-chosen product used with a bit of restraint. Anyone running a full face, body and scalp rotation should expect to spend more, and that's fine. The point isn't frugality for its own sake; it's knowing which part of your routine is eating the budget.
Routine one: the face shelf
| What to look for | What to avoid |
|---|---|
| 30ml or 50ml, 5–10mg per ml | 100ml 'face and body' blends at 1mg per ml |
| Airless pump or narrow dropper | Wide-mouthed jars you dip fingers into |
| Full ingredient list with base oils named | 'CBD complex' with no milligram figure |
A 30ml moisturiser with 300mg, at around £18, gives roughly 60 pumps. That's 30p a go. Used once nightly, you're at about £2.10 a week, and the jar should see you through two months.
Watch the base formula as closely as the CBD. If the first four ingredients are water, glycerin, silicone and fragrance, you are paying a premium for a fairly ordinary moisturiser. A short, fatty-acid-rich base — squalane, shea, jojoba — is where your money earns its keep.
Routine two: the body shelf
Body products are where cost-per-use maths gets humbling. You apply five millilitres to a leg, not half a millilitre to a cheek. A 200ml lotion at 2mg per ml contains 400mg in total, which sounds generous until you realise each full-body application uses around 10mg.
That's not a reason to skip it. It is a reason to stop buying body CBD at £40 a tube and expecting it to last the season. High-street own-brand ranges and online specialists now sit closer to £18–£25 for 200ml at a sensible strength. At £22 for 40 applications, that's 55p per use — about £1.65 a week at three applications.
If you only use body product on dry shins and elbows, buy a smaller size. A 200ml tube has a period-after-opening symbol for a reason, and most of us are not getting through it inside twelve months.
Routine three: the scalp shelf
Scalp products are the most expensive per use and the most over-bought. A 30ml serum at 10mg per ml, £16, used at 1ml per application, gives 30 uses — 53p each. Three applications a week puts you at roughly £1.60.
You rarely need more than a few drops along the parting. If you're saturating your whole head, check whether the dropper is the problem or your technique is. Some people find a weekly treatment easier to justify than a daily one, and the cost maths supports that.
Spotting a weak formulation without opening the box
- No milligram figure anywhere. 'Infused with CBD' and nothing else is a red flag. If the strength isn't stated, it is usually small.
- Suspiciously cheap per mg. Below about 3p per mg, check whether you're buying isolate in a carrier oil, whether the batch has independent testing, and whether the brand is vague about its supply chain.
- CBD low on the ingredient list. Ingredients are listed in descending order of weight until you hit 1%. If CBD appears after the preservative, it's a token amount.
- Aroma doing the heavy lifting. Peppermint, eucalyptus and menthol create a strong sensation that people mistake for efficacy. That tingle is the fragrance, not the cannabidiol.
- 'Full spectrum' with no number. A nice phrase, not a measurement.
Not wasting what you've bought
Store CBD away from the radiator and the bathroom windowsill — heat and light degrade cannabinoids and turn carrier oils rancid faster than you'd think. Use the period-after-opening symbol rather than the printed expiry date as your real deadline. Don't decant a serum into a bigger cream 'to boost it'; you'll dilute the preservative system and end up binning both.
And patch test. A reaction that forces you to throw away a £25 jar destroys the cost-per-use calculation entirely. Inside the elbow, two nights, then decide.
The honest total
A face, body and scalp shelf built on the figures above lands at roughly £5 a week in total, or around £2 if you're running a single product. Either is a reasonable place to be. What isn't reasonable is £45 on a jar you can't calculate the strength of, used twice, forgotten behind the shampoo.
Buy the maths, not the jar.
