Calculate Ovulation in Google Sheets
Formula
The API calculates most fertile days, follicular and luteal phases, and provides a comprehensive fertility calendar with day-by-day fertility levels.
=VERVE("ovulationcalculator", A2)=VERVE.CALL("ovulationcalculator", A2)A2 holds the last_period you're looking up. Drag the formula down and each row resolves on its own.
With literal values
Nothing has to come from a cell — typed values work the same way.
=VERVE("ovulationcalculator", "2024-01-01")Inputs
Required inputs are positional, in the order below. Everything else is passed as a "name", value pair after them — the same shape as SUMIFS.
| Input | Type | Where it goes | Description |
|---|---|---|---|
last_periodRequired | string | argument 2 | First day of last menstrual period (YYYY-MM-DD) (e.g. 2024-01-01) |
cycle_length | integer | "cycle_length", value | Average menstrual cycle length in days (e.g. 28) |
Passing an option
=VERVE("ovulationcalculator", A2, "cycle_length", "28")What lands in your sheet
With no "field" pair the formula spills the whole response as two columns — field name on the left, value on the right — starting at the cell you typed in. Make sure the cells below and to the right are empty.
Pulling one value
Add a "field" pair to get a single cell back instead of a table. The field name is the dot-path from the table below.
=VERVE("ovulationcalculator", A2, "field", "last_period")=VERVE.CALL("ovulationcalculator", A2, "field", "last_period")Available fields
#PREMIUM(field) rather than a value, so a locked field never looks like a real answer.| Use as "field" | Type | Example cell value | Description |
|---|---|---|---|
last_period | string | 2024-01-01 | The first day of the last menstrual period provided |
cycle_length | number | 28 | The average menstrual cycle length in days |
ovulation | object | {…} | Estimated ovulation date and how many days into the cycle it falls |
ovulation.date | string | 2024-01-15 | Calculated ovulation date in YYYY-MM-DD format |
ovulation.days_from_last_periodPremium | number | 14 | Number of days from last period to ovulation |
fertile_window | object | {…} | Range of days conception is possible, with its length |
fertile_window.startPremium | string | 2024-01-10 | Start date of the fertile window period |
fertile_window.endPremium | string | 2024-01-15 | End date of the fertile window period |
fertile_window.duration_daysPremium | number | 6 | Total duration of fertile window in days |
most_fertile_days | object | {…} | The narrower range with the highest chance of conception |
most_fertile_days.startPremium | string | 2024-01-13 | Start date of the most fertile days period |
most_fertile_days.endPremium | string | 2024-01-15 | End date of the most fertile days period |
most_fertile_days.duration_daysPremium | number | 3 | Duration of the most fertile days in days |
fertile_daysPremium | array[6] | list of rows | Array of daily fertility data with levels and descriptions |
fertile_days.0.date | string | 2024-01-10 | |
fertile_days.0.day_relative_to_ovulation | number | -5 | |
fertile_days.0.fertility_level | string | medium | |
fertile_days.0.description | string | Fertile | |
next_period | object | {…} | Estimated start of the next period and how many days away it is |
next_period.datePremium | string | 2024-01-29 | Estimated date of the next menstrual period |
next_period.days_from_last_periodPremium | number | 28 | Days from last period to expected next period |
cycle_phases | object | {…} | The phases of the cycle with their length and what happens in each |
cycle_phases.follicular_phase | object | {…} | From the first day of the period to ovulation |
cycle_phases.follicular_phase.duration_daysPremium | number | 14 | Duration of follicular phase in days |
cycle_phases.follicular_phase.descriptionPremium | string | From first day of period to ovulation | Description of the follicular phase |
cycle_phases.ovulation | object | {…} | The day the egg is released |
cycle_phases.ovulation.duration_daysPremium | number | 1 | Duration of ovulation phase in days |
cycle_phases.ovulation.descriptionPremium | string | Egg is released from ovary | Description of the ovulation phase |
cycle_phases.luteal_phase | object | {…} | From ovulation to the start of the next period |
cycle_phases.luteal_phase.duration_daysPremium | number | 14 | Duration of luteal phase in days |
cycle_phases.luteal_phase.descriptionPremium | string | From ovulation to next period | Description of the luteal phase |
current_status | object | {…} | Where today falls in the cycle, and whether it is a fertile day |
current_status.current_phasePremium | string | Menstruation | Current phase of menstrual cycle relative to today |
current_status.is_fertilePremium | boolean | false | Whether the user is currently in the fertile window |
current_status.days_until_ovulationPremium | number | -701 | Days until ovulation from today (negative if past) |
current_status.days_until_next_periodPremium | number | -687 | Days until next period from today (negative if past) |
disclaimer | string | This calculator provides estimates only. Actual ovulation may vary. Consult a healthcare provider for medical advice. | Medical disclaimer regarding calculator accuracy |
Filling a whole column
Hand the first argument a range instead of a cell and the add-in makes one batched call for the lot, then spills the answers down. That is faster than dragging the formula and costs the same credits — one per row looked up.
=VERVE("ovulationcalculator", A2:A100, "field", "last_period")=VERVE.CALL("ovulationcalculator", A2:A100, "field", "last_period")A2:A100 is the column of last_period values. The result spills down alongside it, one row per input, blanks skipped.
When a cell doesn't fill
A failed lookup returns readable text starting with #ERR rather than a spreadsheet error, because Excel cannot show a custom message on a real error — you would get a bare #VALUE! with no reason. The trade-off is that IFERROR() won't catch it; test with LEFT(cell, 4) = "#ERR" instead.
| Cell reads | What happened |
|---|---|
#ERR Not connected | No API key saved. Open the side panel and connect your account. |
#ERR Replace <name> with a cell or value | The preview formula was copied as-is. Swap the placeholder for a cell reference. |
#ERR No "x" in ovulationcalculator | An option name that this source doesn't take. The message lists the ones it does. |
#ERR No data point "…" | The "field" path isn't in the response. Check the dot-path against the table above. |
#PREMIUM(field) | The field exists but your plan doesn't include it. |
#ERR Out of credits | The month's credits are spent. Usage resets on your billing date. |
Before the formula works
The add-in reads the API key you saved once in the side panel — the key never goes in the formula, so a shared sheet doesn't leak it and a collaborator without access simply sees the last calculated values.
- Install the add-in for Google Sheets or Excel.
- Open the side panel and sign in, or paste a key from your dashboard.
- Type the formula above into any cell.
Other ways to use Calculate Ovulation in Google Sheets
Set up Calculate Ovulation in Google Sheets on VerveSheets, or reach the same source a different way. Your VerveSheets account and credits work on all of them — one key, one balance.
Frequently asked questions
Does Calculate Ovulation in Google Sheets work in both Google Sheets and Excel?
Yes — the same source, the same arguments. Sheets calls it =VERVE("ovulationcalculator", …) and Excel calls it =VERVE.CALL("ovulationcalculator", …); that function name is the only difference.
Do the cells recalculate on their own?
They recalculate when the sheet does — on edit, on open, or on a manual recalc. Each recalculation is a fresh call and spends credits, so for a large static column it's worth copying the results and pasting them as values.
How many credits does a filled column cost?
1 credit per row looked up, whether you drag the formula or pass a range. The range form is one HTTP call instead of many, but the credit count is the same.
Can I share the sheet without sharing my key?
Yes. The key is stored against your account, not in the file. Collaborators see the values already in the cells; formulas only recalculate for someone who has connected their own account.
Why is a cell showing #ERR instead of an error?
So you can read the reason. Excel can't display a custom message on a real spreadsheet error, so the add-in returns the explanation as text on both platforms instead.