Pott Candles · September Maths
For review with Ailis
Working document · actuals to 2026-09-08

This is the working, not the plan. Every figure below is tagged with where it came from, so we can go line by line and agree it or correct it. The numbers that actually change the answer are isolated at the end, with what each one does if it is wrong.

measured pulled from a system, with the source named assumption our judgement, argue with these derived calculated from the rows above it
The answer
3.39x blended ROAS

is breakeven for September at the £260,154 goal. To get there the ads have to deliver 1.93x new-customer ROAS at £35 per new customer. Today they are delivering 1.60x at £42.

Step 0. What a pound of sales is worth

Everything downstream rests on this. Revenue figures include VAT, and two of the largest costs are per order rather than per pound, so a single margin percentage does not work. On the actual mix sold 1 to 08 September:

Per £100 of salesAmountWhere it comes from
VAT-£16.6720% VAT rate measured
Financial dashboard, financials.vatRate
Product cost-£31.6160% blended margin on ex-VAT product revenue measured
Dashboard margins.blended, weighted across 10 SKUs
Fulfilment-£8.91£4.50 per order, 1.98 orders per £100 measured
Dashboard shipping.fulfillmentCostPerOrder
Payment processing-£2.201.7% plus £0.25 per order measured
Contribution£40.61derived This is the 40.6% used everywhere below.

Cross-check: this same calculation reproduces the financial dashboard's own profit line to the penny for every closed month of 2026. January £9,029, February £4,213, March -£4,947, April -£3,403, May -£1,483, June £5,368, July -£387, August £3,726. If this row is wrong, the dashboard is wrong too.

Step 1. The goal sets the ad budget

Fixed overhead is £28,896 a month whatever we spend, so once contribution and overhead are known, everything left is available for advertising. At breakeven, every pound of budget is a pound of profit.

Revenue goal (inc VAT) £260,154 ← client target x contribution 40.6% £105,623 less fixed overhead -£28,896 ------------ = ad budget at breakeven £76,727 BREAKEVEN BLENDED ROAS = £260,154 / £76,727 = 3.39x

The ad budget currently in the sheet is £76,204, which is £523 under that figure. For a month this size those are the same number, so the budget needs no change.

Step 2. Subscription renewals

Ads do not touch this line, so it comes out of the goal first. The forecast is the Recharge schedule multiplied by the share that actually bills, because people skip and churn between the schedule being set and the charge running.

The correction that matters here

Recharge charges contain two different things: renewals, and the first order when a new subscriber signs up. First orders are completed checkouts, so they always bill, and they belong to new customers rather than to this line. Measuring realisation across both together flatters it. Stripping first orders out, using Shopify order tags, and the two sources reconcile to within £1,000 a month:

MonthRenewals scheduledRenewals billedRealised
April£54,995£49,24789.5%
May£49,511£45,36791.6%
June£56,858£51,42090.4%
July£64,134£57,63389.9%
August£54,673£46,14284.4%
September 1 to 8 settled£16,329£13,06380.0%

The rate has fallen every month since May. That is a retention question rather than a forecasting one, but it has to be forecast honestly either way.

September renewalsAmountBasis
Billed 1 to 8 September£13,063Recharge, settled measured
Still scheduled 9 to 30£40,382Recharge queue measured
At September's 80.0% rate£45,368assumption our base case, because the trend is downward
At August's 84.4%£47,145derived if September stops deteriorating
At the April to August pool 89.2%£49,083derived if it recovers to normal
Currently in the sheet£64,427Schedule at about 95%, the best month on record

Step 3. Returning customers

Also outside the ads. Driven by the email and launch calendar, so it is forecast from what those days actually produce rather than from a monthly average.

InputValueWhere it comes from
Measured 1 to 08 September£16,251Shopify, returning customers excluding renewals measured
A day with an email£2,2554 such days so far this month measured
A day without£1,8084 such days so far this month measured
Launch-day multiple4.26x18 real product launches back to 2024, 95,406 orders measured
New-Pott drops specifically: Autumn Scents, New Season, Raku, Teal
12 September, Rust & Amber£8,655derived baseline £2,031 x 4.26
Remaining calendar9 + 13Email days and quiet days left, from the sheet measured
September returning£66,449derived

The launch lift is a one-day event. Across those four new-Pott drops the day after a launch came back to 1.05x of baseline and the day after that to 0.96x, so no multi-day tail is assumed.

Step 4. What is left for the ads

Goal £260,154 less subscription renewals -£45,368 less returning customers -£66,449 ------------ = NEW CUSTOMER REVENUE £148,337 57% of the goal
ValueNote
New-customer AOV£67.83Measured this month, 276 customers measured
New customers needed2,187derived £148,337 / £67.83
Banked 1 to 08 September£18,720276 customers measured
Still to find£129,617derived over 22 days = £5,892 a day
Current run rate£2,340 a daymeasured so the ads must run at 2.52x the pace of the first 8 days

Step 5. The thresholds

Running nowNeeded for the goalGap
Blended ROAS4.04x3.39xabove the line
New-customer ROAS1.60x1.93x+0.33
Cost per new customer£42.29£35-17.0%

Blended ROAS reads comfortably today and that is misleading. We are spending £1,459 a day against a base of subscriptions and repeat customers that arrives regardless, so the base is doing most of the carrying. As spend rises toward £2,957 a day, blended falls toward the 3.39x line by arithmetic alone, whether or not anything changes. The only thing that holds it up is new-customer ROAS.

Step 6. The gap we have to close

Advertising gets less efficient as you spend more, because the cheapest customers are reached first. We have measured that on this account rather than assuming it away: new-customer revenue per day = 5.694 x (spend per day) ^ 0.824. At the breakeven budget that curve predicts:

Curve predictsGoal needsGap
New-customer revenue£109,669£148,337£38,668
New-customer ROAS1.43x1.93x+0.50
Cost per new customer£47£35-26.1%
New customers1,6172,187570 short

That is the whole job: a 26.1% improvement in acquisition cost while roughly doubling daily spend. There is one precedent on this account. The Isle of Wight tomato launch in June moved cost per new customer from £54.14 to £41.06, a 24% improvement, at flat spend. Rust & Amber is the equivalent event, which is why the budget steps on the 12th.

If efficiency does not improve

Ad spendRevenue lands% of goalBlendedProfit
£43,773£180,88670%4.13x£771
£60,000£201,37577%3.36x£-7,138
£76,727 the breakeven budget£221,48685%2.89x£-15,699
£90,000£236,89491%2.63x£-22,717

On current efficiency the month breaks even at about £45,500 of spend and £183,123 of revenue, which is 70% of the goal. The goal and breakeven only happen together if cost per new customer comes in at £35.

The five numbers to argue with

Everything above is either measured or arithmetic, except these. If one of them is wrong, this is what it does to the answer.

Subscription realisation: 80.0% this month

We use September's own rate because the trend has been downward for four months. If it recovers to the April to August average of 89.2%, renewals land £3,715 higher.

If it is wrong: New-customer ROAS needed falls from 1.93x to 1.88x. If the sheet's £64,427 turns out right, it falls to 1.68x, which closes a third of the gap.

Returning-customer forecast: £66,449

Built from 8 days of this month split into email and non-email days, then applied to the remaining calendar. Eight days is a short base.

If it is wrong: 10% either way moves the requirement to 1.85x or 2.02x.

The launch multiple: 4.26x

Median of four new-Pott launches. Rust & Amber is a new pot and a new scent together, which is arguably bigger than any of them, but the sample is four.

If it is wrong: If the 12th performs like an ordinary day, the requirement rises to 2.02x and £6,623 has to be found by the ads instead.

New-customer AOV: £67.83

Measured on 276 new customers this month. It decides how many customers the revenue target converts into.

If it is wrong: A £5 move changes the customer count by about 174, and the CAC target with it.

The response curve: exponent 0.824

Measured on this account from daily spend and new-customer revenue. It sets how much efficiency we lose as budgets rise, and therefore the size of the gap in Step 6.

If it is wrong: It does not change what the goal needs, only how hard the goal is. A flatter curve makes the 26.1% ask smaller.

Where the numbers came from

SourceUsed forWindow
Shopify (order level)Revenue, orders, shipping income, new vs returning split, new-customer AOV1 to 08 September, plus 95,406 orders back to 2020 for the launch study
RechargeSubscription schedule and what actually billed, by day and statusApril to September 2026
Meta and Google AdsDaily ad spend1 to 08 September
KlaviyoCampaign dates, used to identify launch days618 campaign days back to March 2023
Financial dashboardMargin, VAT, fulfilment, payment fees, overheadLive configuration

Actuals are complete to 2026-09-08. Built 2026-09-09. Rebuilt from source on every refresh, so nothing here is typed by hand.