Examples
Examples
Try the starting example
- Periods oldest first: name, distinct donor IDs joined by |; none for zero donors
- P1,A|B|C P2,B|C|D P3,C|D|E
- Donor count by period
- P1: 3; P2: 3; P3: 3
- Retained donors versus preceding period
- P2: 2; P3: 2
- Preceding-period cohort retention (%)
- P2: 66.6666666667; P3: 66.6666666667
- New donor IDs by later period
- P2: D; P3: E
- Lost donor IDs by later period
- P2: A; P3: B
Try another scenario
- Periods oldest first: name, distinct donor IDs joined by |; none for zero donors
- P1,A|B|C P2,B|C|D P3,A|B|C|D
- Donor count by period
- P1: 3; P2: 3; P3: 4
- Retained donors versus preceding period
- P2: 2; P3: 3
- Preceding-period cohort retention (%)
- P2: 66.6666666667; P3: 100
- New donor IDs by later period
- P2: D; P3: A
- Lost donor IDs by later period
- P2: A; P3: None
Calculation method
Calculation method
Donor count by period
Count unique supplied donor IDs; duplicate IDs within one period are rejected.
Retained donors versus preceding period
Size of current/previous donor-set intersection.
Preceding-period cohort retention (%)
Retained/previous donor count×100; undefined when the previous set is empty.
New donor IDs by later period
Current IDs absent from the previous set.
Lost donor IDs by later period
Previous IDs absent from the current set.
Symbols and units
- a
- Periods oldest first: name, distinct donor IDs joined by |; none for zero donors
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Assumptions & limits
Assumptions & limits
- A deterministic cohort-set audit using the same donor identity convention across periods. It does not infer identities, treat transaction counts as donor counts or predict retention.
Are these inputs private?
These calculations run in your browser. A shared link contains the values you choose to share. Only questions submitted to the separate AI finder are sent to OpenAI.
Further reading
Charity Commission: funds and reserves background; no universal reserve target ↗
Background reading; this does not imply endorsement or independent review of SumFizz.