May 1, 2014

Swatch and Cast-On Calculator

Swatch and Cast-On Calculator for Knitting (needles or loom)

Swatching for Gauge.  Three words we don’t like to hear.

Have you read or heard that you need to make a swatch? Or check your gauge?
Don’t be scared. Try our swatch and cast-on calculator
Yes, you will need to knit up a swatch in the yarn you intend to use with the tool (needle or loom) you intend for your project in the main stitch, but to find your gauge from there takes a few simple calculations.  If you simply want to find how many stitches you need for a panel, or even a small section to make a feature in your knitting (say a special stitch or even a 6″ bound off slit for a strap to fit through), you will need to know how many stitches to work, bind off or even cast on.
Below you will find help for that as well as how many rows to get the desired length!  If you have the “stitches per inch” or “rows per inch” from an existing pattern, you can compare those numbers to your numbers and calculate the difference you need. Then add or subtract stitches to achieve the same sizing or also the same as “obtain(ing) gauge”.
Let’s get started!  Use the notes and illustrations below to measure your swatch and calculate.  The first examples contain numbers to help you practice.  We encourage you to use the formula spelled out at the bottom, along with the example numbers in the example figures, to test our answers.  Below the examples are cleared out boxes for you to use for your own swatch measurements.
Please note that directions below are written for our Phone and Tablet app.  We thought best to provide a blog to help others with what we already had. If you would like to download and use the app for your convenience please click here.  It is a free iOS app.  At the bottom of this post is a video showing how to use the app and this calculator.  Should you not have an iOS device you are welcome to print this blog for personal use to use as a guide. It would also be a nice paper to keep as a reference for your projects or a swatch reference for your tools (needles and looms).  We would recommend writing at the top the yarn, tool, stitch and project for your reference. Note that gauge can change slightly with your own mood and tension as well as from yarn to yarn even on the same tools.
**(A note for our metric friendly international users.  The calculations will work the same, just change inches to suit your needs.  Its the ratio that’s important).**

For the Cast-On Calculations:

First make a swatch using the selected project yarn of about 5 inches by 5 inches or 6×6. In making the swatch use the same needles or loom that you intend to use in making the project.
Then measure about a 4 inch by 4 inch area on the swatch. A smaller size measurement may be made. However, the estimate provided by the calculator will be more accurate as the measured area increases.
swatch and cast-on calculator
Enter in the number of stitches counted in the measurement. Then enter the width measured when you counted the stitches.
Swatch and cast-on calculator
Gauge Swatch
Now for first project requirement entry:
Enter the desired width or circumference of your project and for the calculated estimate press: ‘Stitches to Cast-On ->’. If width is a circumference for a snug fit, an adjustment to the number to enter may be needed. For example, for socks measure arround the widest part of foot snugly and substract 1/2 inch then enter this for the desired width.
swatch and cast-on calculator
swatch and cast-on calculator
Cast-On Formula used:

Swatch is S stitches and measures W wide. The stitches per inch is S/W and desired width is dW. The Stitches to Cast-On = (dW x S/W).Divide Stitches counted in swatch by swatch Width measured. Multiply by Desired Width.

So for the example for the above you will take your 4×4 measured area. Write the stitches down in that area which is 20.  Your desire is for a 8″ so your math will take 20 (S) divided by 4 (W) now multiply by 8 (dW or desired width) = Result is to cast-on 40 stitches.
Now for the Rows Calculations:
Measure the swatch number of rows and enter the number of rows and the measured length. Then enter the desired length of project and press ‘Rows needed are->’.
Formula for rows needed = (dL x R/L) where dL is desired length, R is number of measured rows and L is length measured.

Divide Rows counted in swatch by swatch Length measured.  Multiply by Desired Length.

We hope this has helped you today and will be used as a reference. Please bookmark and share this post!
Kristen Mangus
©2014 GoodKnit Kisses
For an electronic/ usable version of this calculator please download the iOS device only app GoodKnit. We apologize for any inconvenience if you do not own one of these devices. For personal use only, We (GoodKnit Kisses) give permission to print out these directions in whole. Please do not make multiple copies to distribute. Downloadable PDF copies can be made available upon request by GoodKnit Kisses for large groups or individuals if needed. Please submit request to with the Subject line “PDFGauge  Calculator”.
Calculations are an estimate of your desired project results. GoodKnitKisses and Sagafuse will not be held responsible for any losses occurred using this application.

Swatch and Cast-On Calculator

also called: swatching, knit swatch, loom knit swatch, check you gauge, make a swatch


also called: swatching, knit swatch, loom knit swatch, check you gauge, make a swatch

Knitting, Loom , , , , , , , , , ,
About Kristen Mangus
Kristen is a multi-talented entrepreneur with a heart as big as Texas. She is the owner of GoodKnit Kisses whose mission is to inspire, encourage and empower people through education and design. She’s built a large and loyal online community of followers by sharing her personal passion for loom knitting, needle knitting, crochet and all things creative through YouTube tutorials, Facebook live broadcasts, blogs and pattern design. Her vision is to leave an inspired crafting world for future generations that continues to teach and reach others. She and her husband, John, have three amazing kids.
  1. If you are making a 6″ square using size 9 needles weight 4 yarn how many stitches do I cast on and how many rows. My squares are coming out not all the same. Thank you. Dorie Karp

  2. Hello I am trying to learn how to CO for top down sweater. Can you please give me an example?

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.