Fast, free, easy-to-use online molecular biology tools
Analyze and optimize DNA sequences, design primers, plan plasmid restriction/ligation setups, and calculate molarity or stock dilutions in your browser.
Available tools
Primer Designer
Design forward and reverse primers from a DNA sequence, estimate melting temperature, check GC%, screen for likely hairpin and primer-dimer issues, and send generated primers to Primer Binding Checker.
Primer Binding Checker
Map where forward and reverse primers bind a DNA template, check primer specificity, detect 5' overhangs, calculate expected amplicon size, and receive primer sets from the design tools.
Sanger Primer Designer
Design Sanger sequencing primer pairs across a selected amplification region, auto-plan reliable read-window coverage, prioritize mutation positions, and send suggested primers to Primer Binding Checker.
ORF & Protein Translator
Translate DNA or FASTA sequences in selected or six-frame views, find ATG-to-stop ORFs, filter searches by region, and reverse-translate proteins into possible or degenerate coding DNA.
Codon Optimizer
Optimize a DNA coding sequence or reverse-translate a protein using expression-host codon usage, CAI-style scoring, GC control, and restriction-site avoidance. Send optimized DNA to Primer Designer.
Ligation Calculator
Calculate the amount of insert DNA needed for vector:insert ligation reactions using fragment length, vector mass, and desired molar ratio. Supports both bp and kb inputs for vector and insert lengths.
Restriction Site Analyzer
Scan DNA sequences or FASTA files for restriction enzyme sites, zero-site enzymes, cut positions, and digest planning. Open the same sequence in Primer Designer or Primer Binding Checker.
Reverse Complement Tool
Generate the reverse complement, complement, reverse sequence, and parsed uppercase DNA sequence from plain-text or FASTA input, with support for IUPAC ambiguity codes.
Molarity Calculator
Calculate single-solute masses, use the protein molarity calculator for kDa conversions, or build multi-solute buffer, media, stock, staining, and assay recipes with stock multipliers and compound search.
Dilution Calculator
Calculate stock and diluent volumes for stock solution dilutions using C1V1 = C2V2, convert compatible concentration units, check available stock limits, and flag very small pipetting volumes.
Motivation
I'm Rohit James, and I recently completed my PhD from IIT Bombay, where I worked on enzyme engineering and cloning for biocatalysis applications. During that time, I kept running into routine tasks that felt more frustrating than they needed to be: designing primers, checking DNA sequences, calculating molarity or dilutions, and moving results between tools.
That is why I built Mol Biology Tools as a free browser-based collection for routine molecular biology tasks. It keeps sequence analysis, primer utilities, and lab calculations together in one place, so you can stay focused on the experiment. Free to use, no logins, no unnecessary steps, and no need to upload or save your sequences to a server.