Molecular Lab Tools calculator
Homology Arm Calculator
Calculate HDR donor length from left arm, edit insert, and right arm sizes for CRISPR repair planning. Use it for classroom work, protocol planning, and quick wet-lab checks before you verify final values independently.
HDR donor summary
Arms are reasonably balanced.
Left 60 bpInsert 3 bpRight 60 bpBalance 100%
Homology Arm Calculator explained
This homology arm calculator adds left arm, intended edit, and right arm lengths to estimate total donor template size.
It also checks whether the two arms are reasonably balanced, which helps catch coordinate mistakes during HDR donor planning.
The tool supports ssODN-style small edits and longer donor-template planning as a first-pass length check.
The calculator handles empty fields, invalid numbers, and common input formatting mistakes. It gives a clear result and a short interpretation so users can decide what to check next. Students can use the page to learn the calculation logic. Lab workers can use it to reduce manual arithmetic errors. Researchers can use it as a first-pass planning aid before confirming the design with the relevant protocol, reagent datasheet, or analysis software.
For background reading, see this trusted reference: supporting educational source.
Homology Arm Calculator worked example
Given a 60 bp left arm, 3 bp edit, and 60 bp right arm, the donor length is 123 bp and the arms are balanced.
The result should be treated as a planning estimate. Always verify critical lab calculations independently before using them in real experiments.
For related planning, you may also use the Knockout Frameshift Calculator or compare the next step with the Editing Efficiency Calculator.
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Practical questions about Homology Arm Calculator
Can I use this result directly in an experiment?
Use the result as a careful planning estimate. Recheck important values with your protocol, instrument settings, and reagent documentation.
Why does the tool show warnings?
The warnings catch common mistakes such as missing required values, impossible negative values, unsuitable sequence characters, or values outside a typical screening range.
Does the tool replace experimental validation?
No. It supports calculation and screening, but final biological performance depends on the sample, assay, protocol, and experimental controls.