It’s budget planning time. Someone suggests 50% Meta, 30% Google, 20% everything else. It looks tidy. But it’s a split of a number nobody has worked out yet. How do you know the total is right?

Set your total marketing budget first, from what your sales leave after costs. Then split it: most to the channel that’s proven to win profitable customers, a share to email and new creative, and a fixed slice for tests. Splitting before you know the total gives you a plan that looks tidy and has no link to profit.

Step 1: find the total

Start with what each order leaves after the costs that rise with every sale: product, shipping and packing, payment fees, and returns. Then take off your fixed costs and the profit you want to keep. What’s left is your marketing budget.

Say a supplement brand sells £180,000 a month, before VAT. Here is where that goes:

£180,000 of sales a monthbefore VAT
52%
19%
12%
17%
  • Product, shipping, fees and returns (52%)£93,600
  • Fixed costs: staff, rent, software£35,000
  • Profit to keep (12% of sales)£21,600
  • Room for marketing£29,800
£180,000 left £86,400 (48%) after product, shipping, fees and returns. Take off £35,000 of fixed costs and £21,600 of profit, and £29,800 is left for marketing.

Call it £30,000. That’s an MER of 6.0:

Sales£180,000
÷
Marketing£30,000
=
MER6.0

Two checks keep this honest:

  • The floor. Ads alone break even at an MER of about 2.1 (£180,000 ÷ £86,400). You’re well above it, so every sale pays its ads.
  • The monthly view. The fixed costs are why you need 6.0, not 2.1. Open the monthly view in the calculator to see that MER for your own numbers.

Try it with your numbers

Your MER floor

Where each order goes

  • Product
  • Shipping
  • Fees
  • Returns
  • Left for marketing

Left for marketing: £24.80 an order

2.02× MER floor. Below this, every sale loses money once the ads are paid.

Aim for 2.4 to 2.6×, 20 to 30% above the floor.

Add your fixed costs (monthly view)

Staff, rent and software don't rise with each sale, so they stay out of the floor. To see the MER you need to cover them too in a month, add them here.

To cover fixed costs as well, this month needs an MER of 2.89×.

A test slice only works if it's big enough to prove something. This tells you how big, to the pound.

Step 2: split it

This is one example split of the £30,000, for a brand where Meta has proven it wins new customers profitably:

£30,000 a monthone example split
43%
28%
12%
10%
  • Meta: main source of new customers (43%)£13,000
  • Google: catch people already searching (28%)£8,500
  • Email: bring customers back (12%)£3,500
  • Creative: keep Meta ads fresh (10%)£3,000
  • Tests: find the next channel (7%)£2,000

Meta here is new customers and retargeting. Google is Shopping, Performance Max and brand search. Email is Klaviyo and running it. Creative is UGC, static and video. Tests might be TikTok or influencers.

If shoppers in your category search before they buy, Google might be the main channel and Meta the second. The order matters more than the exact percentages.

Three rules we follow:

  1. Protect the main channel. Don’t cut it to fund tests unless it has stopped growing as you add spend.
  2. Budget creative as its own line. A Meta budget with no money for new ads goes stale, and then the platform gets the blame.
  3. Fund tests properly, or not at all. A test that’s too small proves nothing. Easier Ads Budgeting works out how much a new channel needs and for how long.

Step 3: move money every quarter

Each quarter, ask:

  • Did MER stay above target?
  • Which channel got better or worse as spend went up?
  • If you cut a channel for four weeks, did total sales drop?
  • What does next quarter’s sales goal need?

Then move money toward the channels where the next £1,000 still brings in profitable sales.

Free tools to go further

Money stuck in a channel that's stopped paying back can't be moved later. Let's find yours now.

Not sure your budget is in the right places? Book a free call and we’ll go through the split with you.

Quick answers

How do I set my total ecommerce marketing budget?

Start from what each pound of sales leaves after product, shipping, payment fees and returns. Take off your fixed costs and the profit you want to keep. What is left is the most you can spend on marketing.

How should I split the budget between channels?

Give most of it to the channel that is proven to win profitable new customers, usually Meta or Google. Then fund the second channel, email and new creative, and keep a fixed slice for tests.

Should email be in the marketing budget?

Yes. Count your email platform, the time or agency fees to run it, and the design work. It is a channel like any other.

How do I know if a channel is getting too much?

Cut its spend by 20 to 30% for four weeks and watch total sales in Shopify. If sales barely move, it had too much. Check your MER every week while you test.

When should I add a new channel?

When your main channel is profitable and stops growing as you add spend, and you can fund a proper test without cutting a channel that works.

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