Reach, Frequency & GRP Calculator
Gross rating points, reach and average frequency for a media plan — from impressions, spots × rating, GRPs bought, measured reach or reach × frequency — with cost per point and CPM, effective reach at 3+, a frequency distribution, weekly weight and the GRPs, impressions and budget needed to hit a reach target.
How it works
GRPs = impressions ÷ audience × 100 = reach% × frequency = spots × average rating; reach ≈ 1 − e^(−k × GRP/100) (k ≈ 0.5 digital, 0.7 mixed, 0.9 mass TV; use measured reach when available); frequency = GRPs ÷ reach; CPP = cost ÷ GRPs; CPM = cost ÷ impressions × 1,000; GRPs for a reach target R = −100 × ln(1 − R) ÷ k; effective reach N+ = reach × P(exposures ≥ N | reached)
Media plans are bought in gross rating points — impressions expressed as a percentage of the target audience, so 300 GRPs means enough impressions to show every person three times. For broadcast, GRPs are simply the number of spots times their average rating. But people are not reached evenly: some see the ad ten times, many not at all. GRPs therefore split into reach (how many different people were exposed) and average frequency (how often). Reach follows a curve of diminishing returns as GRPs climb, which is how the calculator turns a reach target into the GRPs, impressions and budget you need. On a mixed plan that is roughly 70% of a broad audience by 170 GRPs and 80% by 230, and after that each extra point mostly buys repetition. The curve constant can be set for mass broadcast, mixed or fragmented digital plans, or replaced with measured reach. Effective reach counts only people exposed enough times to be influenced — three is the classic threshold — and the frequency distribution shows how many people sit at each exposure level. Cost per point and CPM make plans comparable across channels; cost per person effectively reached is the truer measure.
Worked example
Six million impressions against a two-million-person audience is 300 GRPs. The mixed curve gives about 88% reach (1.76 M people) at a frequency of 3.4. Modelling exposures among those reached, about 58% of the audience saw the ad three or more times. At $120,000 the plan costs $400 per point, a $20 CPM and 7¢ per person reached — and another 100 GRPs would add only 6 points of reach. An 80% reach target needs about 230 GRPs, so this plan already meets it. Bought over 4 weeks, it is 75 GRPs a week.
Frequently asked questions
Where does the reach curve come from?
It is an exponential fit typical of media plans; the constant varies by channel and targeting (about 0.5 for fragmented streaming and social, 0.7 for mixed plans, 0.9 for mass broadcast). Pick the closest preset, set your own constant, or switch to a measured-reach mode when your platform reports unique reach.
How do I calculate GRPs from spots and ratings?
Multiply the number of spots by their average rating. Twenty spots at a 15 rating is 300 GRPs — the same weight as six million impressions against a two-million audience.
GRP vs TRP?
TRPs (target rating points) are GRPs measured against the specific target demo rather than the total population; the arithmetic is identical. Enter the target demo as the audience to get TRPs.
What is effective reach and why does it matter?
It is the share of the audience exposed at least N times — three by the classic rule. A plan with high reach but low frequency may leave most people under-exposed. The calculator models how exposures spread among the people reached, keeping the same average frequency.
How many GRPs do I need for a reach goal?
On an exponential curve, GRPs = −100 × ln(1 − reach) ÷ k. With k = 0.7, 50% reach needs about 99 GRPs, 80% needs 230 and 90% needs 329 — each extra point of reach costs more than the last.
Related calculators
Marketing analytics from the figures entered; attribution windows, platform definitions and sampling vary, so compare like with like over time rather than against generic benchmarks alone.