In answer to the question “what size should handmade soap be?”, a poll of 388 users of homemade soap found a bar size of 3.85” x 3.25” x 1” thick to be the “family favorite”.
But there’s a lot more to the story – especially if you make homemade soap for sale.
Soap Bar “Size” Considerations
- Dimensions (length, width, and thickness for rectangular bars; diameter and thickness for soap pucks)
- Weight (as measured after cure time when most all water weight is gone)
- Shape (rectangular, hourglass, oval, circular and anything custom)
Sizing Rectangular Soap Bars
The most common “full” bar size, for handmade soap, will typically fall between the following parameters…
- Length: 3.5” to 4.25”
- Width: 2.25” to 4”
- Thickness: 0.75” to 1.25”
- Shape: Rectangular (most popular general shape of homemade soaps)
- Weight: 3.5 oz. to 4.5 oz. AFTER six weeks of curing (for cold process soap)
Family Size Bars
Usually when you see packaging that says “family size”, it means there is as much packed into the box as possible. When it comes to family sizing soap, however, each single bar will be a compromise in size.
Remember the story of Goldilocks? Hopefully she washed her grubby little mitts before eating the Bear family’s porridge. And chances are there was just one bar of soap that was just right.
As you will see in a moment, most male respondents preferred larger bars closer to a square shape (4″ x 4″ for example). Most female respondents preferred narrower bars (tall and skinny has been a developing trend).
We found the following to be the most popular full-size bar dimensions, shape, and weight for women and men who use the same bar in the shower.
- Length: 3.85”
- Width: 3.25”
- Thickness: 1”
- Shape: Rectangular (straight cut most popular overall @ 62%; wavy cut @38%)
- Weight: 4 oz. AFTER six weeks of dry curing (for cold process soap)
Soap Bar Size Survey Results
When it comes to sizing any soap bar, the solution comes down to a combination of comfort and longevity. I’m sure you have used soap that splits when it gets thin. This happens with most “true soap”. This means it’s best to start with a bar that has some thickness (at least 0.75″).
Another consideration is how well the bar fits in your hand. If it is too large, you will likely keep dropping it. If it is too small, it’s easy to lose track of and have it slip away while using. Rectangular bars are shaped like a brick – not a stick. They are not naturally easy to hold and manage.
Here are the most popular rectangular soap bar sizes. It is based on a 2019 survey of 388 men and women across the United States.
Please Note: This study is based upon using rectangular soap bars with squared edges. In other words, soap that has been cut from a loaf with no additional refinement done.
| Demographic | Length | Width | Thickness |
| Women 18 to 29 | 4”” | 2.85″ | 1″ |
| Women 30 to 49 | 3.75″ | 3″ | 1″ |
| Women 50+ | 3.75″ | 2.75″ | 1″ |
| Men 18 to 36 | 4″ | 3.9″ | 1.125″ |
| Men 37+ | 4″ | 3.75″ | 1.125″ |
| Common for Family | 3.85″ | 3.25″ | 1″ |
The above chart is a compilation of averages with some important notes.
- The movement toward “tall and skinny” bars factors into the size preferences given. This is especially true with women between the ages of 18 and 49. Several respondents noted this in the comments section so it is worth mentioning.
- Bar thickness for most men was nearly a tie between 1.125” (one and an eight inches) and 1.25” (one and a quarter inches). Overall the split was approximately 52% to 48%.
- Accuracy of feedback will vary. Some people likely measured their bars while others estimated. The request was for “optimal soap bar size” so some may have made mental adjustments. IE/ “I wish this bar was just a little narrower…”
Surprising Results
More than one person responded that they preferred guest soap bars for comfort. Those were removed from the results to accurately provide stats for full-size bar soap. It is worth noting however that a good handful of people like handmade soap in guest bar sizes.
A Note on True Soap
True soap is a distinction made by the United States Food and Drug Administration. It basically means that the soap uses naturally derived glycerin as its cleaning agent rather than artificial chemical detergent. Here is a link to the FDA’s website so you can see exactly what they mean.
The Shape of Soap to Come
The ideal bar size changes depending on shape. Companies like Johnson and Johnson spend a fortune on focus groups to figure out the best soap bar size and shape. The three most popular shapes in bar soap are rectangular, hourglass, and oval.
Luckily for us soap makers, we can easily purchase silicone soap molds to give us intricate hourglass and oval soap shapes. However, the most common bar shape for homemade soap, from a loaf, is rectangular.
There are still fast and easy ways to adjust the shape of a rectangular bar of soap, however they are somewhat limited.
The most common method is to bevel or chamfer all straight edges. This simply means to slightly shave the sharp 90-degree angle sides down at a 45° angle. You can use a bevel or chamfer tool such as the one shown in the video below. You can also use a sharp knife blade with a little practice. Vegetable peelers are also a great way to do this quickly – if you have a steady hand.
A very easy way to get a round or oval bar shape is to use a vertical soap mold. This can be as simple as lining the inside of a Pringles potato chip tube with parchment paper. Of course, there are plenty of vertical soap molds available if you want to get original with shape.
Cheap Soap Puck Vertical Molds Using Plastic Pipe
I went to a local hardware store and bought a ten foot length of 3″ plastic drainage pipe. I paid an extra $5.00 to have it cut into ten pieces at 12″ long each. Now I have ten perfect soap molds for (nearly) 3″ diameter soap pucks.
Important Notes on Using Plastic Pipe as a Soap Mold:
- The inside of the pipe was not quite three full inches. The pipe size is named after its “nominal” measurement. This means the inside will usually be a little bit smaller.
- Although the tubes are each a foot long, I find that going more than 10″ deep of soap does not work well. For me, it gets too difficult to push out more than 10″ of soap.
- Be sure to line the insides of the pipe with parchment paper or a thin flexible plastic sheet. If the soap is in direct contact with the inside of the pipe it can be almost impossible to get out cleanly.
- Consider using a push stick to get your soap out… Do you remember “push ups” ice creams or “push pop” candy? It came in a tube with a stick on the bottom. The stick was connected to a disk inside the tube. The stick and disk acted as a plunger. When you wanted more ice cream or candy to come out of the tube, you just pushed the plunger.
- After the first time I made soap in a piece of plastic pipe, I struggled to get it out. Eventually I found a few 2.5″ wooden disk s left over from a craft project. I glued them together to make the disk stronger then attached it to the top of a long neck wine bottle (don’t judge me 😉
- This was just a prototype but it worked well. I left the bottle on the table, then placed the pipe (filled with now hardened soap) over the disks hot glued to the bottle cap. Pushing down on the pipe I could get about half of the soap exposed out of the tube and pull from there.
Weighing Your Bar Options
Another factor in soap bar size, is its weight. This was not part of the size survey because most people (other than soap makers 😉 ) don’t have a highly accurate digital scale hanging around. And if they did, do they really want to put a semi-used bar of soap on it? Probably not.
The good news is, we don’t need them to weigh their soaps for us. We already know approximate weights. They are based on dimensions and typical oil densities.
Assuming a firm bar (well dried and hardened) at 3.85” x 3.25” x 1”, the wight should be about 4 ounces US. More accurately this would be 3.85 oz. to 4.4 oz. depending on ingredients and final moisture content at time of use.
For cold process soap, the curing process generally removes about 15% of the weight through water evaporation (sometimes more). This means if you made a 5 oz bar and let it cure for 4 to 6 weeks, you will likely end up with a finished weight of about 4.25 oz.
Note: The weight will continue to drop slightly as more water evaporates. That 5 oz bar will probably weigh about 3.8ooz after twelve months of drying/hardening.
Hot process curing typically removes about 5% to 8% of any additional moisture in the bar. This is for typical hot process in which most of the liquid “cooks out” during the soap making process. The soap will be in a gloppy, non-fluid state when molding and will not pick up fine detail in the mold.
Insider Tip:
If you add a lot of extra liquid to hot process soap batter to make it easier to work with, it can actually take longer than cold process soap to fully harden. This is because the saponification process has completed, and the thermal reaction will not be available to help evaporate the liquid. It’s okay to add liquid to make a more fluid pour – just be aware that it will take a long time to fully harden.
>>> Get the Inside Edge
When determining what size soap bars you wish to sell, also consider your packaging options and if you want to do something special to make your soap more unique. There is a post on this site that will help make your homemade soap stand out... 5 Genius Ways to Make Your Soap Stand Out
In Closing
What matters most is that your soap bars are a comfortable size and shape for the user. I suggest you do not get too hung up on ensuring every bar is the exact same size. By its very nature, handmade soap will vary as well the final bar sizes. That is one of the things that make homemade soap unique.