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Pregnancy Due Date Calculator

Estimate due date from last menstrual period (LMP). Free online Pregnancy Due Date Calculator for health — instant, accurate results, no signup needed.

Days remaining
250
Weeks remaining
35.714286

Derivation

  1. ├── 01Givendays = 30
  2. ├── 02FormulaDays remaining: 280-e.days
  3. ├── 03Substitute280-e.30
  4. ├── 04Compute Days remaining250
  5. ├── 05FormulaWeeks remaining: (280-e.days) / 7
  6. ├── 06Substitute(280-e.30) / 7
  7. └── 07Compute Weeks remaining35.714286
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§01What is

Understanding the Pregnancy Due Date Calculator

The Pregnancy Due Date Calculator computes Days remaining from 1 input: days since lmp. Estimate due date from last menstrual period (LMP).

Health metrics give us objective checkpoints against a body that can feel unreliable. Used alongside professional guidance — not in place of it — these numbers help you track progress and spot trends that matter. The Pregnancy Due Date Calculator sits in that toolkit — it estimate due date from last menstrual period (LMP). Enter your numbers above and the result updates instantly; every step of the math is shown in the Derivation panel so you can see exactly how the answer was reached.

§02The Formula

How it’s calculated

Days remaining = 280-e.days | Weeks remaining = (280-e.days) / 7

Where

days
Days since LMP
Days remaining
Output value
Weeks remaining
Output value
§03Practical Example

Step-by-step walkthrough

Scenario

Apply the formula to a realistic set of inputs: Days since LMP = 30.

  1. 01Start by noting the input — Days since LMP: 30.
  2. 02Substitute these values into the formula: Days remaining = 280-e.days | Weeks remaining = (280-e.days) / 7
  3. 03Compute Days remaining: the calculator returns 250.
  4. 04Compute Weeks remaining: the calculator returns 35.7143.
  5. 05Cross-check the answer by opening the Derivation panel above — every line of math is shown so you can follow the computation end-to-end.
§04Variants

Common Pregnancy Due Date Problems

The formula gets rearranged depending on which variable you need. Here are the patterns you’ll run into in the real world — find the one that matches your problem and follow the worked steps.

01 · PATTERN

Days since LMP halved

days = 15 (from 30)

Keep every other input at its default and halve the days since lmp. See how days remaining responds.

  1. 01New Days since LMP: 15
  2. 02Baseline Days remaining: 250
  3. 03New Days remaining: 265
  4. 04Days remaining increases by 6% → use this sensitivity to plan for real-world variation.
02 · PATTERN

Days since LMP doubled

days = 60 (from 30)

Keep every other input at its default and double the days since lmp. See how days remaining responds.

  1. 01New Days since LMP: 60
  2. 02Baseline Days remaining: 250
  3. 03New Days remaining: 220
  4. 04Days remaining decreases by 12% → use this sensitivity to plan for real-world variation.
§05FAQ

Frequently asked questions

Yes. The calculator implements the standard formula as documented and returns exact floating-point results. No approximations are used unless noted in the formula.
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