Enter Last menstrual period (LMP), Current date and Cycle length (days) and the remaining scenario settings to review gestational age with this tool. Weeks-and-days notation describes elapsed time, so 10 weeks and 4 days is not 10.4 decimal weeks.
Age = Current date − Date of birth, adjusted for whether the birthday has occurred this year.The calculation links Last menstrual period (LMP), Current date and Cycle length (days) to gestational age. Weeks-and-days notation describes elapsed time, so 10 weeks and 4 days is not 10.4 decimal weeks. Different reference methods include different starting assumptions.
Enter Last menstrual period (LMP), Current date and Cycle length (days) and the remaining scenario settings to review gestational age with this tool. Weeks-and-days notation describes elapsed time, so 10 weeks and 4 days is not 10.4 decimal weeks.
Calculate elapsed pregnancy weeks and days from the selected dating reference. Keep gestational age separate from time since conception.
Weeks-and-days notation describes elapsed time, so 10 weeks and 4 days is not 10.4 decimal weeks. Different reference methods include different starting assumptions.
Prepare Last menstrual period (LMP), Current date, Cycle length (days) and Method. Select the reference type, enter its date and check the date for which gestational age is requested.
Weeks-and-days notation describes elapsed time, so 10 weeks and 4 days is not 10.4 decimal weeks. Different reference methods include different starting assumptions. Uncertain dates and clinician-established dating can change interpretation. The calculator cannot evaluate fetal development or pregnancy health.
Use the full settings in the worked-example table. They produce Gestational Age: 10 weeks 0 days. Compare the method and units as well as the displayed number.
The displayed relationship is Age = Current date − Date of birth, adjusted for whether the birthday has occurred this year. Select the reference type, enter its date and check the date for which gestational age is requested.
Uncertain dates and clinician-established dating can change interpretation. The calculator cannot evaluate fetal development or pregnancy health. For personal care, discuss the measurements and method with a qualified clinician.
Worked gestational age calculator example. Set Last menstrual period (LMP) = 2026-01-01; Current date = 2026-03-12; Cycle length (days) = 28; Method = Naegele's Rule (LMP). The corresponding output is Gestational Age: 10 weeks 0 days. Weeks-and-days notation describes elapsed time, so 10 weeks and 4 days is not 10.4 decimal weeks.
Calculate elapsed pregnancy weeks and days from the selected dating reference. Keep gestational age separate from time since conception.
Select the reference type, enter its date and check the date for which gestational age is requested.
| Field | Example value | Entry check |
|---|---|---|
| Last menstrual period (LMP) | 2026-01-01 | Use the calendar date for this scenario; keep the comparison date explicit. |
| Current date | 2026-03-12 | Use the calendar date for this scenario; keep the comparison date explicit. |
| Cycle length (days) | 28 | Use the stated unit and the measurement required by this model. |
| Method | Naegele's Rule (LMP) | Select the method before interpreting the result; different modes answer different questions. |
Relationship used for this example: Age = Current date − Date of birth, adjusted for whether the birthday has occurred this year.
Weeks-and-days notation describes elapsed time, so 10 weeks and 4 days is not 10.4 decimal weeks. Different reference methods include different starting assumptions.
| Output | Displayed result |
|---|---|
| Gestational Age | 10 weeks 0 days |
With these settings, gestational age is 10 weeks 0 days. Use the same units and calculation mode when reproducing this example.
Weeks-and-days notation describes elapsed time, so 10 weeks and 4 days is not 10.4 decimal weeks. Different reference methods include different starting assumptions. Uncertain dates and clinician-established dating can change interpretation. The calculator cannot evaluate fetal development or pregnancy health.
Replace the illustrative last menstrual period (lmp) value (2026-01-01) with your own value, then complete the other inputs for the same scenario. Select the reference type, enter its date and check the date for which gestational age is requested.