How it works
The quick overview
If you've landed here looking for a pregnancy weeks calculadora, good news — Pregnancy Weeks calculadora runs in your browser, shows the working, and doesn't try to sell you a spreadsheet template.
Trend matters more than a single reading — note today’s and compare in six weeks. Have last year’s figures to hand — then work out the number and the rest of this page explains what the answer means.
Work out gestational age in weeks and days from the LMP date or an ultrasound-estimated conception date.
Worked through on one example
Let's walk a concrete example through Pregnancy Weeks calculadora.
Work out gestational age in weeks and days from the LMP date or an ultrasound-estimated conception date.
Scenarios where Pregnancy Weeks calculadora pays off
Pregnancy Weeks calculadora is aimed at people arriving with questions like these:
- "How many weeks pregnant"
- "Gestational age calculadora"
- "LMP to weeks"
- "What is pregnancy weeks"
- "How to calculate pregnancy weeks"
- "Pregnancy weeks formula"
When it isn't the right tool
Every tool has an edge where it stops being the right answer. Pregnancy Weeks calculadora is no exception:
- For legally binding tax or medical decisions — cross-check with HMRC, NHS or a qualified professional.
- For very large or very small extremes the rounding error outgrows the useful precision.
- When the underlying rate or threshold has changed since the page was last reviewed — always verify with the primary source.
- When the input you have is already a derived figure (net of something) — feeding it in as "gross" will double-subtract.
Where this calculation usually breaks
Every time you work out the number for a new scenario, one of these creeps in — it's worth knowing them ahead of time.
- Mixing up units — grams in one field, ounces in another, then wondering why the answer is off.
- Treating a percentage as a whole number. 20% means 0.20 in the maths, not 20.
- Rounding at every step. Keep four decimals internally and only round the final number.
- Using last year's thresholds. If the page isn't dated, assume it's stale and check GOV.UK.
- Reading a tool like this as advice. It is maths, not a decision — the decision is still yours.
The sources behind the numbers
Where the maths needs an external authority, we cross-check against:
- NHS
- ACOG
Works well alongside
If this question keeps coming up for you, the same cluster of tools usually comes next:
- Pregnancy Due Date calculadora — Estimate your due date from LMP using Naegele's rule (+280 days) or from conception date, with current-week and trimester guidance aligned to NHS dating.
- Pregnancy Weight Gain calculadora — Estimate healthy weight gain across pregnancy trimesters based on pre-pregnancy BMI and number of babies.
- Fertile Window calculadora — Estimate the fertile window (typically 5 days before and 1 day after ovulation) from cycle length and last period date.
- Ovulation calculadora — Predict your fertile window and ovulation day based on cycle length and last period — uses the 14-days-before-next-period midpoint.
How we keep this accurate
Our calculadoras run on pure, unit-tested functions — the same logic lives in the browser and in the CI test suite. When tax rates, thresholds or official figures move, the update lands within 24 hours of the announcement. You can read the editorial policy and corrections policy.
Found an out-of-date number on Pregnancy Weeks calculadora or anywhere else in the Health toolkit? Send it to the editorial desk and we'll patch it. Or browse the full calculadora directory for the next tool you need.