Media planning & forecasting glossary

Plain-English definitions of the concepts behind forecast-led media planning. Each entry explains what the term means and why it matters when you decide where the next pound of budget should go.

iROAS

Incremental return on ad spend - the revenue advertising genuinely creates, not what it is credited with.

Marginal ROAS

The return on the next pound of spend - the metric that should govern whether a channel is worth scaling.

Hill function

The curve used to model how channel response flattens as spend approaches saturation.

Adstock

How advertising impact carries over after exposure, creating delayed commercial effect.

Saturation curve

How channel performance flattens as spend rises - the relationship behind diminishing returns and budget ceilings.

Diminishing returns

Why each additional pound of spend tends to return less than the one before it.

Budget ceiling

The spend level beyond which a channel can no longer return profitably.

Scenario planning

Modelling best, base and worst case outcomes before budget is committed.

Paid media forecasting

Predicting the commercial outcomes of a paid plan before spend is committed.

Ad spend forecasting

Modelling how budget changes translate into performance, channel by channel.

Incrementality

The outcomes advertising genuinely caused, not those it was merely credited with.

Forecast accuracy

How close predictions land to actual results, and how much to trust a forecast.

Confidence interval

The range a forecast is expected to fall within, expressing uncertainty honestly.

Media planning

Deciding where, when and how much to spend across channels to hit an objective.

Budget allocation

Splitting a fixed budget across channels by marginal return rather than habit.

Attribution

How credit for a conversion is assigned across the touchpoints that preceded it.

Media mix modelling

Estimating each channel contribution from aggregate data - a privacy-durable alternative to user-level attribution.

Budget reallocation

Moving committed budget between channels by marginal return, not average performance.

Customer acquisition cost (CAC)

How much it costs to acquire a new customer from marketing and sales spend.

Cost per lead (CPL)

The cost of generating an enquiry - and how it differs from cost per customer.

LTV:CAC ratio

Customer lifetime value against acquisition cost - the clearest test of sustainable growth.

POAS (Profit on Ad Spend)

Profit on ad spend - what advertising returns after costs, not just revenue.

Break-even ROAS

The minimum ROAS where ad revenue covers product cost and fees.

ROAS

Return on ad spend - revenue per pound of advertising, and why the average can mislead.

Creative fatigue

The decline in ad performance as an audience sees a creative too many times.

Creative testing

Systematically testing concepts and variants to find winning creative.

Creative refresh

Introducing new creative before performance declines, on a planned cadence.

Creative volume

How many concepts and variants you need to test, refresh and scale paid social.

Frequency

How often an average person sees an ad - the most direct driver of fatigue.

Hook rate

The share of viewers who watch past the first few seconds of a video ad.

Thumb-stop rate

The rate at which scrolling users stop on an ad - the first gate of attention.

Creative iteration

Evolving winning creative into new variants rather than starting from scratch.

Statistical significance

The confidence that a measured difference is real, not noise - vital for testing.

These ideas come together in marginal ROAS vs average ROAS and in our free planning tools.