Most small nonprofits start digital acquisition backward. They pick a budget (“let’s try $2,000 on ads”), run the campaign, and then stare at the results trying to decide if $95 per new donor is good or terrible.
You can’t answer that question after the fact unless you answered a different one first: what is a new donor actually worth to us, and how much of that value are we willing to spend to get one? That number is your allowable cost per acquisition. Once you have it, every acquisition decision gets easier, from whether to run a Meta campaign to whether a lead-generation offer is working.
Here’s how to calculate it with data you already have.
A new donor is worth less than their first gift suggests (at first)
The trap is judging a donor by their first gift. If someone gives $80 and it cost you $95 to acquire them, the campaign looks like a loss. Sometimes it is. But that donor might give again next year, and the year after that.
Or they might not. That’s the part most organizations skip. The M+R Benchmarks 2026 study found that new online donor retention was 24% in 2025, while donors who had given before were retained at 66%. Put plainly: if you acquire 100 new online donors this year, roughly 76 of them may not give again next year.
So a new donor’s value isn’t their first gift, and it isn’t their first gift times ten years of loyalty. It’s somewhere in between, and you can estimate it.
Build a simple five-year model
You need four inputs:
- Average first-year giving per new donor. Pull donors acquired online in a recent year and total their giving in their first 12 months. Divide by the number of donors.
- Your first-year retention rate. Of those donors, what share gave again in the following year? If you don’t have enough history, the 24% benchmark is a reasonable starting point.
- Your retention rate after that. For donors who made it past year one, what share keep giving each year? The 66% benchmark for prior donors is a reasonable placeholder.
- Cost to serve a donor for a year. Receipts, thank-you letters, a newsletter, appeals. Even a rough figure like $10 a year is better than zero.
Now run it forward. Imagine a food pantry that acquires 1,000 new online donors who give an average of $80 a year and cost $10 a year to serve. Using 24% first-year retention and 66% retention after that:
| Year | Active donors | Net revenue | Cumulative net |
|---|---|---|---|
| 1 | 1,000 | $70,000 | $70,000 |
| 2 | 240 | $16,800 | $86,800 |
| 3 | 158 | $11,088 | $97,888 |
| 4 | 105 | $7,318 | $105,206 |
| 5 | 69 | $4,830 | $110,036 |
Over five years, each new donor is worth about $110 in net revenue. In year one alone, about $70.
This is a simplified model. It assumes every retained donor gives the same amount, applies one retention rate to everyone after year one, and doesn’t discount future dollars. Real donors upgrade, become monthly donors, or give once and vanish. But a simple model you actually use beats a precise one nobody builds. If you want to go further, our guide to calculating donor lifetime value walks through a more detailed version.
Turn the value into a spending rule
Knowing a donor is worth $110 over five years doesn’t mean you should pay $110 to get one. That’s break-even, and only if every assumption holds. You need a decision rule that fits your cash position.
I’d think about it in three zones:
- Up to year-one value ($70 in the example). You get your money back within the first year. Most organizations can defend this to a board and a finance committee.
- Between year-one and five-year value ($70 to $110). You’re investing. The money comes back over time, assuming your retention holds. This makes sense if you have reserves and a real plan to keep new donors.
- Above five-year value. You’re losing money on acquisition unless something else is going on, like donors who become monthly or major donors at an unusually high rate. You’d want evidence before spending here.
Write the rule down before you launch anything. “We’ll pay up to $70 per new online donor, and up to $90 if we can show our second-gift rate is above 30%” is a rule a board can understand.
Your retention rate changes your budget
Run the model again with 30% first-year retention instead of 24%. Five-year value per donor rises from about $110 to about $120.
That’s a smaller jump than many people expect. It’s real money across 1,000 donors (about $10,000), but it’s a reminder that retention improvements pay off slowly. The bigger point is the reverse: if your actual first-year retention is well below 24%, your allowable cost is lower than you think, and an acquisition campaign that “worked” may not have.
So check your own number. If you’ve never measured it, why year-end donors disappear by March is a useful look at where first-time donors tend to fall away.
Compare channels on the same yardstick
Once you have an allowable cost, you can compare very different acquisition efforts fairly.
Say a paid social campaign brings in new donors at $85 each. A lead-generation campaign brings in email subscribers at $3.64 each (the average Meta cost per lead in M+R’s advertising benchmarks), and 3% of them donate within a year. That’s about $121 per donor. A peer-to-peer event brings in donors at $40 each, but you don’t yet know how many of them will give again.
Without an allowable cost, these are three unrelated numbers. With one, you can see which fit your rule and which need to improve. Track every channel the same way: total cost divided by new donors acquired, then compare that to your value model. Cost per click and cost per lead are useful for managing a campaign, but they don’t answer whether it was worth it.
Do this before your next campaign
Block two hours this week. Pull every donor whose first gift came online in a recent year. Calculate their average first-year giving and how many gave again the next year. Plug your numbers into the table above and write down your year-one and five-year value per donor.
Then write a single sentence: “We’ll pay up to $___ for a new online donor.” Bring it to your next budget conversation. It won’t be perfect, but it’ll be the first time your acquisition spending has a standard to meet.
