4 Amazingly Accurate Pregnancy Calculators (Updated 2018)


Modern technology has afforded us many advancements that make estimating due dates a little easier nowadays. That being said, the best methods for estimating when your bundle of joy might arrive require no fancy equipment. Many tools and calculators exist online now that make the estimation process easy for parents-to-be. Some of them even retro-date the calculations to tell parents what day they most likely ovulated and conceived.

Realistically, only around 5 percent of women deliver on their due dates, per Parenting Magazine. Still, so much focus is placed on that single day in time. When it passes mothers by, it often creates a lot of unnecessary stress. Whether it’s a first or fifth baby, Moms should be encouraged to embrace their due date as a range in which their baby will be born. Their little one might show up a few weeks before that day, or a few weeks after it. Refraining from referring to such are “early” or “late” can sometimes help women to adjust the way they see birth and the fetal development process.

4 Amazingly Accurate Pregnancy Calculators

1. The Menstrual CycleBest Due Date Calculator

The simplest way of calculating your estimated due date is going off of your menstrual cycle. Every cycle, and for most women, every month, you release an egg. If fertilization occurs during this ovulation period, then implantation soon follows and usually by the time you’re expecting your next period, you’re getting a positive pregnancy test. There is some confusion among many women as to why they’re considered four weeks pregnant at this point in time. Essentially, the two extra weeks are added so care providers can cover all their bases, because it’s easier to go by when your last period was than try to guess when you ovulated

after the fact.

You can also use the date you started your last period to determine an estimated due date by counting backward three months and adding one week. For example, if your last period started on June 15th, you count back three months to March 15th, and then add one week making your estimated due date March 22nd. The most time-consuming option would be to count ahead 280 days from the date of your last period.

[Read more about Pregnancy Test]

2. Ultrasound Calculations

Best Due Date Calculator

Dating a pregnancy by ultrasound is a common practice, albeit not as solid as going off of menstrual dating. However, many women have irregular periods or get pregnant unexpectedly and aren’t sure when their last cycle started or when they ovulated. Some are pregnant for several weeks or months without even knowing they are. In these cases, ultrasound dating is the next best choice. One study published in the journal Acta Obstetrica et Gynceologica Scandinavia shows that ultrasounds performed during the thirteenth week are the correct most often for dating purposes, having a 98.3 percent accuracy rate.

To date a pregnancy in the first trimester, a transvaginal sonogram will most likely be the method used. While this is uncomfortable for some women—usually more so because of the procedure rather than physical pain—it’s the only way to get a clear picture of the womb that early on when it is still deep within the pelvis. The bonus is that transvaginal sonograms don’t require you to drink a gallon of water beforehand and hold your bladder until they call you from the waiting room.

During the procedure, measurements will be taken of the developing fetus. Combined, these figures will correlate to the estimated due date. Keep in mind that dating by ultrasound is only as good as the technician that’s performing it. Being off by even one millimeter can alter the date by a day, and when you’re in those first 14 weeks, the baby is quite small in size. Remember, the due date is just a guess.

3. Hiccups Along the Way

Certain issues do arise in some pregnancies that warrant the need to push baby out a little sooner than he or she was intending — or even what Mom and Dad were intending. Induction or schedule cesareans may be necessary if:

  • Poor blood supply to the placenta
  • Placental calcification
  • Known birth defects
  • Maternal illness that could worsen with childbirth or be passed onto the baby
  • Placenta previa is present
  • Uterine scarring poses too much of a risk of rupture with contracting

4. Letting Your Baby DecideBest Due Date Calculator

Slowly but surely, the medical industry has led women astray from trusting their own body’s abilities. Biologically, your body and your baby work in tandem and know the perfect time to start the cascade of hormonal responses that trigger the start of labor. Birth has been transformed from a miraculous and natural event that virtually all women are born capable of into one which is met with hesitation because it is painted as a painful and unpredictable rite of passage that women must suffer through at the mercy of whatever options their medical treatment facility or care provider allows.

Physicians like to see babies delivered during the 41st week of pregnancy in most cases, but this isn’t what the science of birthing actually supports as being the best avenue for the baby to take. Midwifery Today reports studies comparing birth outcomes between women who delivered within the medically-accepted two week range of their due dates and those who went overdue showed no significant differences in perinatal mortality; in fact, it was slightly higher at 0.75/1000 in the on time group than the overdue group at 0.56/1000.

[Read more about Overdue]

Barring any of the unforeseen events noted above, it’s perfectly find to let that baby “cook” until they are ready to make their grand entrance on their own. Consider the waiting period and the experience of being nine to ten months pregnant a testament to the level of patience parenthood will often require. If your due date is approaching or has already passed, remind yourself it’s just a guess. Remember that stress produces cortisol and adrenaline, which can actually stall labor and keep you from dilating. Breathe, relax, and get lots of rest. You’ll need it.


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