Culture Needed
50g
Medium
950 ml
Ferment
24 hr
24 hr
72°F
Every 1d
Ready now
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Inputs
Result
1,000 ml × 5% = 50g grains needed. You have exactly 50g — ready to brew. Medium: 1,000 - 50 = 950 ml milk.
Inputs
Result
500 ml × 20% = 100g starter needed. You have 100g — ready now. Feed 1:2:2 ratio (starter:flour:water).
Use 5% kefir grains by volume (50g grains per 1 liter of milk). Healthy grains grow about 5% per batch, so they’ll gradually increase. If your grains are too few, the kefir will be thin and under-fermented. Too many grains makes overly sour, thick kefir in just a few hours.
| Culture | Ratio | Ferment Time | Feed Interval |
|---|---|---|---|
| Milk Kefir | 5% | 24 hr | Daily |
| Yogurt | 3% | 8 hr | Weekly |
| Sourdough | 20% | 12 hr | Daily |
| Kombucha | 10% | 7 days | Weekly |
Most cultures grow with each feeding cycle. Kefir grains grow ~5% per batch (double in ~2 weeks). Sourdough doubles with each feeding. Kombucha SCOBY grows a new layer each week. To grow 50g of kefir grains to 200g, you need about 28 daily feedings (28 days).
Each culture has an optimal temperature range. Kefir and water kefir prefer 68–75°F (room temperature). Yogurt needs 105–115°F for proper incubation. Sourdough is most active at 75–80°F. Kombucha ferments best at 75–85°F. Cheese cultures vary widely by type.
Most cultures can be backed up for emergencies. Kefir grains survive 2–3 weeks in the fridge in fresh milk. Sourdough starter can be dried and stored for months. Kombucha SCOBY keeps in a 'hotel' (jar of strong tea) for months. Yogurt starter can be frozen in ice cube trays for 3–6 months.
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Last Updated: Mar 19, 2026
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.