| Metric | Value | Copy |
|---|---|---|
| {{ r.label }} | {{ r.value }} |
| Week | Start | End |
|---|---|---|
| {{ row.w }} | {{ row.s }} | {{ row.e }} |
| Milestone | Date |
|---|---|
| {{ m.name }} | {{ m.date }} |
Pregnancy due dates are calendar estimates that connect the start of a pregnancy to a likely birth window. They help plan appointments and prepare support at home and at work so you can organize the next months with less guesswork.
Enter either the date of the last period or a conception date, then review the estimated due date together with weeks of gestation, days remaining, and trimester. You can also preview fetal length and weight by week and copy neatly formatted summaries for your records.
A common flow is to use the last period, leave the default settings in place, and note the due date and trimester span. If cycle length differs from the usual pattern, adjust the cycle field so the calendar aligns better with your history.
Results are estimates and real timelines vary. Use consistent dates and units, repeat entries if details change, and treat the output as planning guidance only. This tool provides informational estimates and does not substitute professional advice.
The calculator models gestational age and an estimated due date from a start reference. The reference is either the last menstrual period or a conception date that is converted to an equivalent reference. Outputs include the due date, gestational days and weeks, a trimester label, remaining days, and a lightweight projection of fetal length and weight by week.
The core computation anchors all dates to a base start date and adds a configurable gestation length. When the last period is used, the cycle length adjustment shifts the due date relative to a base cycle. When the conception method is selected, an internal two‑week offset is applied for gestational age calculations.
Trimester labeling follows week bands of zero to twelve, thirteen to twenty seven, and twenty eight to forty. Progress is the fraction of gestational days completed, expressed as a percentage with one decimal place, and remaining days are the difference between the configured gestation and days elapsed.
Where B is the base start date, D is the due date, T is the gestation length in days, C is the cycle length, C₀ is the base cycle, O is an optional calendar offset, G is gestational days, and X is an internal offset used only when the conception method is selected.
| Symbol | Meaning | Unit/Datatype | Source |
|---|---|---|---|
| B | Base start date (LMP or conception adjusted) | date | derived |
| D | Estimated due date | date | derived |
| T | Gestation length | days | input |
| C | Cycle length | days | input |
| C₀ | Base cycle (reference) | days | input |
| O | Due date offset | days | input |
| G | Gestational age | days | derived |
| X | Gestational offset for conception method | days | constant (=14) |
| Threshold Band | Lower Bound (weeks) | Upper Bound (weeks) | Interpretation | Action Cue |
|---|---|---|---|---|
| 1st trimester | 0 | 12 | Early development window. | Confirm dates and early scans as advised. |
| 2nd trimester | 13 | 27 | Mid pregnancy milestones. | Plan screening and anatomy scan. |
| 3rd trimester | 28 | 40 | Late preparation period. | Finalize support and time off. |
| Field | Type | Min | Max | Step/Pattern | Error Text | Notes |
|---|---|---|---|---|---|---|
| Method | select | — | — | last | conception | — | Choose calculation basis. |
| Date | date | — | — | yyyy‑mm‑dd | Invalid date. | Required to compute results. |
| Cycle length | number | 10 | — | 1 | — | Warning if outside 10 to 60; tooltip cites 24 to 35 typical. |
| Gestation length | number | 250 | 310 | 1 | — | Warning if far from 250 to 310. |
| Base cycle | number | 20 | 60 | 1 | — | Reference for cycle adjustment. |
| EDD offset | number | — | — | 1 | — | Shifts the due date by days. |
| Working days per week | number | 0 | 7 | 1 | — | Used to estimate working days left. |
| General warnings | — | — | — | — | Due date is before the start date. | Shown when inputs conflict. |
dd/mm/yyyy using the device locale fallback when needed.| Input | Accepted Families | Output | Encoding/Precision | Rounding |
|---|---|---|---|---|
| Start date | Date picker value | Formatted dates | dd/mm/yyyy strings | Calendar day |
| Numbers | Integers | Percent, counts | 1 decimal for percent | Floor or nearest as above |
| Export | CSV, JSON | Summary, timeline, milestones | Plain text | Exact values |
Computation runs in your browser and no server requests are made for entered data. Clipboard and download actions create local files and copies only.
No data is transmitted or stored server‑side. This tool provides informational estimates and does not substitute professional advice.
Pregnancy due dates and trimester timing are calculated from a start reference and simple options.
You now have a dated plan you can revisit and adjust as details change.
No. All calculations run in your browser and files are created locally. Nothing is uploaded or retained on a server.
Clipboard access may prompt for permission.It is an estimate based on entered dates and settings. Real timelines vary and clinical recommendations may differ.
Use it to plan, not to diagnose.Dates show as dd/mm/yyyy. Length shows centimetres or inches and weight shows kilograms or pounds based on the unit switch.
Yes. After the page loads, calculations do not require a connection because they use only your local device.
First is weeks zero to twelve, second is thirteen to twenty seven, and third is twenty eight to forty.
The conception method converts the date to a last period reference and then applies a two week offset to gestational days.
Yes. You can copy CSV to the clipboard or download CSV and JSON summaries for sharing or record keeping.
Values near a band edge can label either side after rounding. Focus on the date span rather than a single day.