Wash pears, remove stems and cores, and chop into small pieces (no need to peel).
Place chopped pears and water in a large stockpot. Bring to a boil, then reduce heat and simmer for 20–25 minutes until pears are soft.
Pour mixture into a cheesecloth-lined strainer over a large bowl. Let drip for several hours or overnight without pressing (for clear jelly).
Measure exactly 4 cups of pear juice into a clean pot.
Stir in lemon juice and powdered pectin. Bring to a rolling boil over high heat, stirring constantly.
Add sugar all at once and return to a full rolling boil. Boil hard for 1 minute while stirring.
Remove from heat and skim off foam if necessary.
Ladle hot jelly into warm, sterilized jars, leaving ¼ inch headspace.
Wipe rims clean, apply lids and bands fingertip tight.
Process jars in a boiling water bath canner for 10 minutes (adjust for altitude if needed).
Remove jars and let cool undisturbed for 12–24 hours. Check seals before storing.
