Calculating postage by weight is one of the best ways to create an accurate shipping estimate, but weight is just one piece of information that you will need in order to narrow down the potential cost of shipping. You will also need to know the package dimensions, the destination zip code, how quickly you want it to arrive and whether or not you'll be purchasing insurance.

You also need to know which shipping service you plan to use because each has its own rates and online calculators. Learn everything you need to know in order to calculate postage by weight and set up a ballpark shipping cost for your products.

## Invest in a Postal Scale

One of the best investments you can make for calculating shipping costs is a sturdy digital postal scale. In a pinch, your bathroom scale can work for larger items, and a food scale can work for small items. However, it's unrealistic to do large-scale product shipment preparation without a scale meant for the job.

A postal scale can read large and small weights in both metric and imperial/standard if you have a preference. It also goes to at least two decimal places for accuracy. The platform on which packages sit is wide, flat and capable of balancing even awkwardly shaped packages. A digital output is often more convenient to read and makes your preparation more efficient.

## How to Weigh a Package on a Postal Scale

Start by packaging your item in its final box and include all the bubble wrap and paper that it requires for padding. You don't need to close and tape the box at this point if you're just trying to get an estimate, but it is important that you don't make the mistake of just weighing the item itself. The cardboard box and bubble wrap contribute a small but significant weight to the overall package.

With nothing on the weighing platform, turn on the scale and push the "tare" button. The screen should read "zero." Make sure your scale is set to your preferred unit (metric or imperial/standard) and then place the package on the platform. The numbers may jump around a little bit, but that's normal. Wait for the numbers to settle and/or the scale to beep.

Write down the weight and unit. Make sure the scale goes down to zero between each package. Next, you'll need to get a few other measurements before you can finish estimating the shipping cost.

## Measuring the Package

In addition to the package's weight, its size and shape also influence the shipping cost. Larger, bulkier items cost more to ship. Before you can use an online postage calculator for weight, you need the length, width and height of the package. In the case of nonrectangular packages, you also need to record a measurement of girth.

A soft fabric tape measure offers more flexibility in obtaining measurements than a hard plastic ruler, but either will do just fine for rectangular packages. Be sure to start measurements at zero, not at the end of the tape. The length should be the longest measurement.

In addition to length, width and height, measure the girth for cylindrical or pyramidal packages. Take your soft measuring tape completely around the widest part of the package body to obtain the girth measurement.

## Know the Destination Zip Code

The destination zip code represents the final piece of information you'll need in order to use a postage shipping calculator. That's because it requires more time and resources to ship an item 3,000 miles versus 300 miles. However, if you are trying to calculate shipping so that you can list the item for sale online, you don't know the destination zip code yet, which poses a problem.

Instead, you'll want to do a little bit of investigating. Select three areas of the country that represent far-away destinations and obtain their zip codes. For example, if you live in Illinois, you might choose zip codes in California, Florida and Maine. Enter these zip codes plus a zip code closer to home in the postage calculator one at a time in order to get a range of shipping estimates that can help you decide what to charge for shipping.

## Use Online Postage Calculators by Weight

Now that you're armed with the package's weight, dimensions and destination zip code, you can go online to use a postage calculator. At this point, it helps to have an idea of which shipping service you want to use to send your package. The United States Postal Service, United Parcel Service and FedEx remain among the most popular options in the U.S. If you don't have a preference, you can easily use each one's online postage calculator to do a price comparison.

On either the USPS, UPS or FedEx website, navigate to the shipping calculator. You'll be asked to enter information about your package, the destination and your own zip code.

When inputting the weight and dimensions, pay close attention to the units selected. If your postal scale gave the weight in grams, choose metric. If the weight was in pounds and ounces, choose standard/imperial. Likewise, make sure you choose inches or centimeters accordingly.

## Comparing the Shipping Results

Once you've filled out the shipping calculator, you'll see a chart that explains your shipping options. It costs more money to send a package overnight than it does to put it on ground transport. If you're not facing a time crunch, you can select the cheapest option. Otherwise, compare the prices and the arrival times to select a service with which both you and the recipient will be happy.

Then, go to the competitor's websites and compare their prices and arrival times as well.

## When Weight Calculations Aren't Affordable

Did you know that using a postage calculator by weight isn't the only option? If you have a relatively small but heavy item, flat-rate shipping might save you money. All three of the major U.S. shipping services offer their own version of flat-rate shipping, in which you pay for the box, not for the shipping. Some limits apply because the boxes are only made for certain sizes, and UPS, for example, has a 70-pound weight limit for its flat-rate service.

It also helps to become familiar with the additional shipping services on offer. For example, if you're trying to sell your used college textbooks, you know how heavy they can be and might worry about charging the right price for shipping. However, USPS offers Media Mail, which is an affordable, flat-rate shipping option. Shipments do have to adhere to certain restrictions to qualify for Media Mail, and it's not a lightning-fast service.

## Other Price Factors to Consider

Finally, keep in mind that other factors can cause the shipping cost to go up. Shipping internationally, for example, always involves much higher fees. If the item you're shipping is valuable, it might be worthwhile to purchase insurance in case of any accidents. Therefore, calculating postage by weight is just the first step.