Overview
Includes current cycle status, days until ovulation, and educational information about cycle phases, perfect for fertility tracking and family planning applications.
Live Test Calculate Ovulation Source →
Formula
One function covers the whole catalog: the first argument names the source, the rest are its inputs, and the "field" pair says which single value lands in the cell. Formulas covers the grammar that applies to all of them.
=VERVE("ovulationcalculator", A2, "field", "disclaimer")=VERVE.CALL("ovulationcalculator", A2, "field", "disclaimer")A2 holds the last_period you are 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", "field", "disclaimer")=VERVE.CALL("ovulationcalculator", "2024-01-01", "field", "disclaimer")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. Premium inputs are accepted on every plan but only take effect on plans that include them.
| Input | Type | Where it goes | Description |
|---|---|---|---|
last_periodRequired | string | argument 2 (A2) | First day of last menstrual period (YYYY-MM-DD) date |
cycle_lengthOptional | integer | "cycle_length", value | Average menstrual cycle length in days default 28 · range 21–35 |
Passing an option
=VERVE("ovulationcalculator", A2, "cycle_length", 28)=VERVE.CALL("ovulationcalculator", A2, "cycle_length", 28)What lands in your sheet
The "field" pair is what makes the formula resolve to one cell. Its value is a dot-path from the table below, so swapping it is how you pull a different value — one formula per column.
Seeing everything at once
Drop the "field" pair and the formula returns the whole response instead: two columns, field name on the left and value on the right, spilling from the cell you typed in.
=VERVE("ovulationcalculator", A2)=VERVE.CALL("ovulationcalculator", A2)The second row's table would land on top of the first's, and every cell after the first reads #REF! (#SPILL! in Excel). Keep one per sheet, or name a field, and leave the cells below and to the right empty.
Response fields
Paths are relative to data. Each one is exactly what the "field" pair accepts, so swapping it is how you pull a different value into a cell. On a plan without a Premium field the cell reads #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] | Array of daily fertility data with levels and descriptions | |
fertile_days.0.datePremium | string | 2024-01-10 | Date of the fertile day in YYYY-MM-DD format |
fertile_days.0.day_relative_to_ovulationPremium | number | -5 | Days relative to ovulation date (negative before, positive after) |
fertile_days.0.fertility_levelPremium | string | medium | Fertility level classification: low, medium, high |
fertile_days.0.descriptionPremium | string | Fertile | Human-readable description of fertility status for day |
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
Both platforms make one batched call for a column rather than one request per cell, and both cost the same — 2 credits per row looked up. How you write it differs, because the two runtimes batch at different points.
=VERVE("ovulationcalculator", A2:A100, "field", "disclaimer")In Google Sheets, give the arguments ranges and the answers spill down from the cell you typed in. Custom functions there run synchronously and in isolation, so dragged cells cannot be coalesced — the range form is how a column becomes one call. The "field" pair is required here: a per-row two-column table has nowhere to spill. Use a full column per input (A2:A100, not A2) — a single-cell reference is read as row 1 only and the rest of the column comes back blank.
In Excel, type the formula once and fill down — no range form and none needed, because its runtime is asynchronous and the add-in coalesces the calls a fill produces into a single batched request. Do not hand VERVE.CALL a range: Excel flattens it into positional arguments, so A2:A100 arrives as a hundred separate arguments and the cell reads #ERR rather than filling.
Either way, column A holds your last_period values and the answers land beside them, one row each, blank rows 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() will not catch it; test with LEFT(cell, 4) = "#ERR" instead. Error handling covers the rest.
| 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 | A preview formula was copied as-is. Swap the placeholder for a cell reference. |
#ERR No "x" in ovulationcalculator | An option name this source does not take. The message lists the ones it does. |
#ERR No data point "…" | The "field" path is not in the response. Check it against the table above. |
#PREMIUM(field) | The field exists but your plan does not include it. |
#ERR Out of credits | The cycle'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 does not 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.
Use cases
- Fertility Tracking
- Build fertility tracking applications with accurate ovulation predictions based on cycle length and last period date
- Conception Planning
- Calculate conception probability windows and most fertile days to help users plan or prevent pregnancy
- Menstrual Health
- Create menstrual health apps with ovulation tracking, fertile window identification, and cycle insights
- Family Planning
- Provide family planning tools with science-based ovulation calculations and fertility awareness features
Other ways to use Calculate Ovulation
Set up Calculate Ovulation on VerveSheets, or reach the same source a different way. Your VerveSheets account and credits work on all of them — one key, one balance.
Related
More in Lifestyle: