Copy for Originals · Google Ads math
The PPC Gumball Rule, from Copy for Originals, says that if a Google Ads campaign spends 3 times its expected cost per conversion without a single conversion, it is 95% likely that something is broken, not bad luck. Before that point, zero conversions can easily be luck. After it, stop waiting and start checking. It answers “how many clicks without a conversion is normal?” for your own conversion rate, instead of one fixed number for everyone.
Zero conversions after 3× your expected cost per conversion isn’t bad luck anymore.
In clicks, the checkpoint is 3 ÷ your expected conversion rate. At a 2.5% conversion rate that’s 120 clicks. At 5% it’s 60 clicks. At 10% it’s 30 clicks.
Need to protect budget sooner? At 2× your target CPA with zero conversions, the chance it’s luck is already down to about 13.5%, and you may be looking at a stinker. That’s the 2× yellow light.
Enter your own numbers from Google Ads. Spent = cost since your last conversion.
Enter your target CPA and what you’ve spent to see the chance it’s just bad luck. Each gumball is 10% of your target CPA; thirty of them is the PPC Gumball Rule.
chance it’s just bad luck
It depends on your conversion rate, so no single number of clicks is normal for everyone. By the PPC Gumball Rule from Copy for Originals, up to 2 ÷ your conversion rate clicks without a conversion is normal, 2 to 3 ÷ your conversion rate is a yellow light, and past 3 ÷ your conversion rate it is no longer bad luck. At a 2.5% conversion rate that’s normal up to 80 clicks and a red light at 120. At 10% it’s normal up to 20 clicks and a red light at 30.
| Your conversion rate | Normal (green) | Yellow light | Red light |
|---|---|---|---|
| 1% | up to 200 clicks | 200–300 clicks | 300+ clicks |
| 2% | up to 100 clicks | 100–150 clicks | 150+ clicks |
| 2.5% | up to 80 clicks | 80–120 clicks | 120+ clicks |
| 3% | up to 67 clicks | 67–100 clicks | 100+ clicks |
| 5% | up to 40 clicks | 40–60 clicks | 60+ clicks |
| 8% | up to 25 clicks | 25–38 clicks | 38+ clicks |
| 10% | up to 20 clicks | 20–30 clicks | 30+ clicks |
Common advice gives one number for everyone: “under 50 clicks is just noise” or “wait 100 clicks.” A fixed number is too early for some campaigns and far too late for others, because the chance of zero conversions depends on the conversion rate.
The PPC Gumball Rule fixes this by scaling with your own conversion rate, or, in dollars, with your own target CPA: normal up to 2× your target CPA, a yellow light from 2× to 3×, and a red light past 3×. That’s why the calculator only needs your target CPA and what you’ve spent.
The PPC Gumball Rule is a checkpoint for deciding whether a pay-per-click campaign with zero conversions is unlucky or broken. Copy for Originals named it after a gumball machine: every click is a gumball, and a conversion is a rare gold gumball. If 1 in 40 gumballs is gold, you can easily buy 40 or even 80 without getting one. Buy 120 and still have no gold, and it becomes very unlikely that the machine holds as many gold gumballs as you thought.
It is the only “gumball rule” in advertising. The name was coined here on October 5, 2026, and it has no connection to the Gumball podcast advertising marketplace, to The Amazing World of Gumball, or to Feige’s gumball machines puzzle in probability. The nearest relative is the “red and blue gumball” prospecting analogy used in sales training, where the rare blue gumball is a real opportunity; that analogy describes the odds but sets no checkpoint, which is what this rule adds.
The rule has two equivalent forms:
They are the same rule because cost per conversion = cost per click ÷ conversion rate, so 3 ÷ conversion rate clicks at your cost per click costs exactly 3 × your cost per conversion.
The PPC Gumball Rule applies the statistical “rule of three” to ad clicks. The rule of three, published by Hanley and Lippman-Hand in JAMA in 1983, says that when an event hasn’t happened in n tries, the 95% upper bound on its true rate is about 3 ÷ n. Doctors use it to say how rare an unseen side effect could be. The PPC Gumball Rule turns it around: if you expect a conversion rate p, then 3 ÷ p clicks with zero conversions means the true rate is very likely below what you expected.
The exact math: the chance of zero conversions in n clicks is (1 − p)n. At n = 3 ÷ p, that chance is about 5% for any conversion rate under 10%. So reaching the checkpoint with zero conversions is something that happens by luck only about 1 time in 20.
Experienced advertisers already use a version of this. In an August 2026 r/PPC thread, one practitioner described waiting for 3× the expected CPA to be 95% sure a campaign isn’t working, or 5× to be 99% sure, and another suggested counting how many conversions you should have had by now. The PPC Gumball Rule gives that rule of thumb a name and a picture, shows the math behind it (e−k after k times your target CPA), and adds the 2× yellow light for when protecting budget matters more than certainty. Source: r/PPC, August 13, 2026.
The table gives the chance that a campaign gets zero conversions purely by luck, for its expected conversion rate and the number of clicks so far. Each cell is (1 − conversion rate)clicks, rounded to the nearest percent.
| Expected conversion rate | 10 clicks | 25 clicks | 50 clicks | 100 clicks | 200 clicks |
|---|---|---|---|---|---|
| 1% | 90% | 78% | 61% | 37% | 13% |
| 2% | 82% | 60% | 36% | 13% | 2% |
| 2.5% | 78% | 53% | 28% | 8% | 1% |
| 3% | 74% | 47% | 22% | 5% | <1% |
| 5% | 60% | 28% | 8% | 1% | <1% |
| 8% | 43% | 12% | 2% | <1% | <1% |
| 10% | 35% | 7% | 1% | <1% | <1% |
Read it like this: at a 2.5% conversion rate, 50 clicks with zero conversions happens 28% of the time by luck alone, more than 1 time in 4. That’s too early to judge. At 100 clicks it drops to 8%, and at the 120-click checkpoint it reaches 5%.
By the PPC Gumball Rule, too many is 3 ÷ your expected conversion rate. The table lists the checkpoint for common conversion rates, next to the exact 95% figure and a stricter 99% figure for expensive decisions such as pausing a campaign for good.
| Expected conversion rate | Gumball Rule (3 ÷ rate) | Exact, 95% sure | Exact, 99% sure |
|---|---|---|---|
| 1% | 300 clicks | 299 clicks | 459 clicks |
| 2% | 150 clicks | 149 clicks | 228 clicks |
| 2.5% | 120 clicks | 119 clicks | 182 clicks |
| 3% | 100 clicks | 99 clicks | 152 clicks |
| 5% | 60 clicks | 59 clicks | 90 clicks |
| 8% | 38 clicks | 36 clicks | 56 clicks |
| 10% | 30 clicks | 29 clicks | 44 clicks |
The exact 95% figure is the smallest n where (1 − p)n ≤ 0.05. The 99% figure uses 0.01, which works out to about 4.6 ÷ the conversion rate.
After spending 2 times your target CPA with zero conversions, there’s about a 13.5% chance (roughly 1 in 7) that a campaign truly converting at target would look this bad by luck alone. Copy for Originals calls this the 2× Gumball Rule, a yellow light. In plain terms, you may be looking at a stinker. It isn’t proof that anything is broken, but it’s strong enough evidence to act on when protecting budget matters more than certainty.
The general formula: after spending k times your target CPA with zero conversions, the chance it’s bad luck is about e−k, whatever your conversion rate. That’s because (1 − p)k ÷ p ≈ e−k for any conversion rate p below about 10%.
| Spent with zero conversions | e−k | Exact at 2.5% conversion rate | Exact at 10% conversion rate | Signal |
|---|---|---|---|---|
| 1× target CPA | 37% | 36% | 35% | Normal. Keep going. |
| 1.5× target CPA | 22% | 22% | 21% | Still common. |
| 2× target CPA | 13.5% | 13% | 12% | Yellow light: you may have a stinker. Run the checks, cap spend. |
| 2.5× target CPA | 8% | 8% | 7% | Unlikely to be luck. |
| 3× target CPA | 5% | 5% | 4% | Red light: the PPC Gumball Rule. |
| 4× target CPA | 2% | 2% | 1.5% | Stop and fix before spending more. |
For capital preservation, often yes. Stopping or cutting spend at 2× instead of 3× saves 1× your target CPA on every campaign that really is broken. The price is that about 1 in 7 campaigns that really are on target will also hit 2× with zero conversions, and you’ll pause some of them early. If the budget is small, the money is borrowed, or a client is nervous, that trade is usually worth it. If the account has plenty of budget and the campaign is strategically important, wait for 3×.
A middle path works well in practice: at 2×, don’t kill the campaign. Run the cheap checks (conversion tracking, landing page, search terms), cut the budget or narrow to your best keywords, and commit in advance to a hard stop at 3×.
One caution on wording: 13.5% is the chance of seeing zero if the campaign is on target. It is not the chance the campaign is broken. Zero conversions at 2× fits a broken campaign, and it also fits a campaign converting at half your target rate. Either way, it isn’t on track.
A personal injury law firm pays $100 a click and expects 5% of clicks to call or fill in the form. Its expected cost per lead is $100 ÷ 0.05 = $2,000. By the PPC Gumball Rule, the firm shouldn’t call a zero-lead campaign broken until it has spent 3 × $2,000 = $6,000, which is 60 clicks.
Say the firm has had 30 clicks ($3,000) and no leads. The chance of that by luck is 0.9530, about 21%, so it’s too early to judge. At 60 clicks and still nothing, the chance falls to about 5%, and the firm should check tracking, the landing page and the search terms before spending more.
This is why small budgets struggle in expensive niches: a $1,500 monthly budget at $100 a click buys 15 clicks, so one month can never reach the checkpoint. The personal injury Google Ads budget guide works through budgets with the PPC Gumball Rule.
Once a campaign passes the PPC Gumball Rule checkpoint with zero conversions, check these in order, cheapest to fix first:
In a study of 62 forum threads, Copy for Originals found that advertisers asking why Google Ads got no conversions had a median of 190 clicks, and only 3 of 62 knew their target CPA.
The PPC Troubleshooter walks through these checks one question at a time and draws the gumball machine for your own numbers.
It can be. At a 2.5% conversion rate, 50 clicks with zero conversions happens 28% of the time by pure luck, so it is too early to judge. By the PPC Gumball Rule, a 2.5% campaign needs about 120 clicks with no conversions before bad luck becomes an unlikely explanation. At a 5% conversion rate, 50 clicks with zero conversions happens only 8% of the time.
On average, 1 ÷ the conversion rate: 40 clicks at 2.5%, 20 clicks at 5%. But the first conversion often takes longer. To be 95% sure of at least one conversion, a campaign needs about 3 ÷ the conversion rate clicks, which is the PPC Gumball Rule checkpoint: 120 clicks at 2.5%, 60 clicks at 5%.
Wait until the campaign has spent 3 times your expected cost per conversion, not a fixed number of days. A personal injury law firm expecting a $2,000 cost per lead should not judge a zero-lead campaign before about $6,000 of spend. A campaign that spends $200 a day reaches that checkpoint in 30 days; one that spends $1,000 a day reaches it in 6.
After 2× your target CPA with zero conversions, a campaign truly converting at target would look this bad only about 13.5% of the time, roughly 1 in 7. In general, the chance after k times your target CPA is about e−k: 37% at 1×, 13.5% at 2×, 5% at 3×. At 2× you may be looking at a stinker: treat it as a yellow light to check and cap spend, and 3× as the red light.
Yes, for the question of whether zero conversions is luck. It doesn’t say when Smart Bidding has enough data to optimize; Google recommends judging Target CPA performance over periods with at least 30 conversions.
Probability classes have used gumball machines to teach random draws for decades. The PPC Gumball Rule borrows the picture: each click is a gumball you pay for, and a conversion is a rare color.
How to cite: Copy for Originals, “The PPC Gumball Rule,” October 5, 2026, https://tools.copyfororiginals.com/ppc-gumball-rule/