I’m horrible at math, so I created two sourdough starter calculators. I figured I would make them available here on my blog in case you need them, too!

Sourdough Starter Ratio Calculators

The first calculator allows you to enter how much starter you need, and you can choose your own feeding ratio.

The second calculator is for those who don’t really know what feeding ratio to use. Just choose when you want your starter to be ready to bake with, and the calculator will suggest the amount of starter, flour, and water to use.

If you want to learn ALL the details about feeding ratios – what they are, what the numbers mean, how you can use them to your advantage – check out this guide: The Ultimate Guide to Sourdough Starter Feeding Ratios

P.S.: I have another calculator to help with baker’s percentages and hydration level if you need it. Find it here: Sourdough Baker’s Percentage & Hydration Level Calculator

Sourdough Starter Feeding Ratio Calculator

Here’s a calculator to help you figure out how much starter, flour, and water to use with your desired feeding ratio:

Results:

How to use this calculator:

  1. In the first box, type how many grams of starter you want to make. This can be any number, based on your recipe.
  2. In the second through fourth boxes, input the ratio you want to use, like 1 to 1 to 1 (equal parts starter, flour, and water) or another ratio like 1 to 5 to 5 (1 part starter, 5 parts flour, 5 parts water). Experiment with different ratios for different peak windows. A 1:5:5 is my favorite ratio – I do this morning and night!
  3. Click ‘Calculate’. The calculator will show you exactly how much starter, flour, and water you need in grams to make the total starter amount you entered.

Useful material: Is My Sourdough Starter Ready to Bake With? How I Can Tell

Sourdough Starter Feeding Ratio Calculator (Select Your Timeframe)

If you have no clue what feeding ratio you want, this calculator lets you choose how far in the future you want your start to peak.

If you want your starter to be ready in 7 hours, as an example, select the 6-8 hour option. The calculator automatically picks the right feeding ratio for you and lets you know how much starter, flour, and water to use.

Results:


Fine print: this calculator makes assumptions based on averages for a 75°F/24°C home. You may need to adjust up or down based on your lived experience or if your home is warmer or cooler than mine. The strength of your starter will also greatly impact these averages.
The calculations used are as follows: 1:1:1 – 4 to 6 hours, 1:2:2 – 6 to 8 hours, 1:3:3 – 8 to 10 hours, 1:4:4 – 10 to 12 hours, 1:5:5 – 12 to 14 hours, and 1:10:10 – 16 to 24 hours.

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24 Comments

  1. Thank you for these calculators. They are great. Might I make a small suggestion though. It might be a good idea to build a little waste into your calculator. For example. If I use the second calculator and say I want 200g of starter in 16-24 hours it suggests 10g starter, 95g flour, and 95g of water. This will exactly equal 200g of starter but inevitably you will lose some of that. If you built in a small amount of waste (could be identified in the notes) and said 20g starter, 100g flour, and 100g water then you will definitely get 200g of starter to use. Just a thought.

    1. Yes that’s an excellent point. About 20g inevitably sticks to the side to the jar, plus you may want some leftover to feed for your next bake. I’m not sure if I should build that into the calculator or let the user decide how much extra they want – it could cause confusion. Let me think on that one. But great idea.

  2. I’m new to sourdough, so I have a question regarding hydration. I get confused when a recipe says 100% hydration in the starter. How do I know how much to feed in order to get 100%?

    1. So that’s just referring to the fact that it’s a liquid starter. 100% hydration means the flour and water are equal. I only clarify 100% hydration to ensure everyone knows the recipe is using a liquid starter. There are also “stiff” starters, which are not liquid – they basically look like bread dough and are kneaded by hand to mix. You don’t see that many recipes using a stiff starter, but they are out there!

    2. As far as I understand 100% hydration starter means same amount of flour and water as starter, so basically feeding ratio 1:1:1.

      1. Equal parts water and flour is 100% hydration. The flour and water doesn’t have to be the same as the starter – just the last two numbers of the ratio. 1:1:1 and 1:5:5 are both 100% hydration.

  3. This is amazing! I spent months just guessing how much starter I would get and how long it would take to reach the peak. I even thought I had a non-active starter because I never saw it rising as I was only feeding at night.

  4. I’m so glad I found this! It has helped me so much especially when I need my starter to peak 8-10 hours after feeding so it won’t fall before I get home from work! Thank you!

  5. How do you “measure out” the amount of starter you need to feed each time? Do you know the weight of your empty jar, and just discard until you reach the right weight? On the other hand, are you always switching from one jar to the other each time you feed? It just seems that I am constantly making a mess.

    1. Yeah I usually start with a new, empty jar when I’m weighing my feeds. Or I’ll pour out most of what’s in the jar to my discard jar. And what’s left, I’ll scoop up onto my spatula, zero out the scale, and add the bit on top of my spatula back in. It would probably be smarter to weigh my jar, now that you say it… haha

  6. The calculators are great! Now, for those using tools like the Brod & Taylor Home for the starter, how might you integrate temperature into these calculators?

    1. I don’t have one of those tools, so I can’t do any experiments with it. The times in the second calculator are based off a 75F home and many experiments I’ve done. If your temperature is higher than that, the timing will be a little faster.

  7. We all know not every flour has the same observation so what’s the best way to figure out the hydration for my flour? The flour I’m using seems like need more water more than recipe ask for. I have to add like 20 to 25 sometime 30 g extra water to the recipe. Thx in advance.

  8. I love your calculator. It has simplified my sourdough worries.
    If I would like to feed my starter twice how would I adjust the feeding calculations so I don’t stay with too much extra, just enough to put refrigerate for future sourdough projects.

    1. Hey Gendy, glad it’s helpful! If I want a little extra starter, I just add 20-30g to the amount I need. So if a recipe calls for 250g of starter, I’ll make enough for 280g. Then, I’ll have 30g leftover to either feed or put in the fridge.

  9. Thank you for these calculators. I’m very new to sourdough bread making, so I don’t have everything ingrained in my brain just yet.

    1. Don’t feel like you have to. Most of us wing it in the beginning and slowly build on our knowledge as we make mistakes or see things we want to improve. I’m excited for you!! Sourdough is so fun!

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